 |
||||
| 2007 JASN IMPACT FACTOR 7.111 | HOME AUTHOR INFO EDITORIAL BOARD SUBSCRIBE FEEDBACK ALERTS HELP | |||
| CURRENT ISSUE | ARCHIVES | JASN Express | ONLINE SUBMISSION | |
|
||||
| 2007 JASN IMPACT FACTOR 7.111 | HOME AUTHOR INFO EDITORIAL BOARD SUBSCRIBE FEEDBACK ALERTS HELP | |||
| CURRENT ISSUE | ARCHIVES | JASN Express | ONLINE SUBMISSION | |
*
Centre for Nephrology, University College London, London, United
Kingdom
Department of Biochemistry and Molecular Biology, University College
London, London, United Kingdom
Autonomic Neuroscience Institute, Royal Free and University College
Medical School, University College London, London, United Kingdom
Centre National de la Recherche Scientifique URA 1859, CEA Saclay, Gif sur
Yvette, France.
Correspondence to Dr. Robert J. Unwin, Centre for Nephrology, Institute of Urology and Nephrology, The Middlesex Hospital, Mortimer Street, London, W1N 8AA, UK. Phone: 0207-504-9302; Fax: 0207-637-7006; E-mail: robert.unwin{at}ucl.ac.uk
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
In the kidney, reverse transcription-PCR (RT-PCR) studies have demonstrated the presence of P2Y2 and P2Y4 receptor mRNA in most segments of the nephron (23). Functional studies have also demonstrated that UTP and ATP generate calcium signals along the whole renal tubule (23,24,25,26); however, these agonists are equipotent at the rat P2Y2 and P2Y4 receptors, and whether the signals involve one or the other (or both) of these receptor subtypes cannot be determined. It is also not possible to know whether responses are mediated via apical or basolateral membrane receptors, because P2Y2 receptor-specific immunoreactive sites were recently observed in both membranes of inner medullary collecting duct (IMCD) cells (27). In addition, ATP- and UTP-sensitive receptors were detected in both the luminal and basolateral membranes of the mouse cortical collecting duct (CCD) (28).
Relatively little is known regarding the function of P2Y6 receptors, although recent reports suggested that UDP-sensitive receptors can activate ion channels in a variety of polarized epithelia, such as sweat gland (12,15,29), gallbladder (20), pancreatic duct (22), and nasal (13) cells. Northern hybridization studies detected P2Y6 receptor mRNA expression in several different tissues (e.g., spleen, placenta, thymus, intestine, and blood leukocytes), but expression was observed at a very low level in the kidney (5,6). However, it is possible that this receptor has only limited distribution within the nephron and that Northern analysis of whole-kidney extracts could not detect this. Therefore, the aim of this study was to screen for P2Y6 receptors in segments of the rat nephron. The RT-PCR technique was used to study the distribution of mRNA; because specific antibodies directed against the rat P2Y6 receptor are not yet available, we analyzed the functional expression of the protein by measuring inositol phosphate (IP) production and associated changes in [Ca2+]i in response to UDP. Our results demonstrate that P2Y6 receptor mRNA is expressed in most segments of the rat nephron but basolateral expression of the protein, as assessed functionally, is restricted to the proximal tubule, where the receptor is coexpressed with the P2Y1 receptor.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The following segments were studied: nonlocalized proximal convoluted tubules (PCT) taken from the kidney cortex or, when specified, S1 segments identified on the basis of functional criteria (see the Results section), proximal straight tubules taken from medullary rays along the S3 portion of the proximal tubules, type II thin descending limbs (DTL) of juxtamedullary nephrons, thin ascending limbs (ATL), cortical thick ascending limbs, medullary thick ascending limbs (MTAL), CCD, outer medullary collecting ducts (OMCD), and IMCD. DTL, MTAL, and OMCD were all isolated from the inner stripe of the outer medulla.
Extraction of mRNA
RNA was extracted from microdissected segments by using a micromethod
(30) adapted from the
guanidinium thiocyanate-phenol/chloroform method
(31). Briefly, pools of
individual segments were photographed for length determinations before being
transferred, with 5 to 10 µl of microdissection medium, into 400 µl of
denaturing solution (4 M guanidinium thiocyanate, 25 mM sodium citrate [pH
7.0], 0.5% sarcosyl, 0.1 mM ß-mercaptoethanol, 20 µg of yeast tRNA).
After phenol/chloroform extraction and isopropyl alcohol precipitation, the
final pellet was vacuum-dried and resuspended in RNA dilution buffer [10 mM
Tris-HCl [pH 7.6], 1 mM ethylenediaminetetraacetate, 2 mM dithiothreitol, 40
U/ml ribonuclease inhibitor (RNasin; Promega, Madison, WI)]. It was previously
determined that the yield of this extraction procedure was >90%
(30).
RT-PCR
Specific primers were selected from the sequence of the rat P2Y6
receptor cDNA and from the sequence of the human glyceraldehyde-3-phosphate
dehydrogenase (GAPDH) cDNA by using Oligo Primer analysis software (Medprobe,
Oslo, Norway). The sequences of the P2Y6 receptor primers were
5'-TGCTTGGGTGGTATGTGGAGTC-3' (positions 868 to 889) for the
forward primer and 5'-TGGAAAGGCAGGAAGCTGATAAC-3' (positions 1206
to 1184) for the reverse primer. The sequences of the GAPDH primers were
5'-GCCATCAATGACCCCTTCAT-3' (positions 154 to 173) for the forward
primer and 5'-GAGGGGGCAGAGATGATGAC-3' (positions 434 to 415) for
the reverse primer.
For each segment, mRNA extracted from 1-mm tubule length (approximately 60 pg of mRNA) was reverse-transcribed for 50 min at 42°C with 0.5 µg of oligo(dT)12-18 primer, using a first-strand cDNA synthesis kit for RT-PCR (Superscript II RNase H- reverse transcriptase; Invitrogen Ltd., Paisley, UK). After denaturation at 95°C for 3 min, the resulting product was used as a template with the PCR Core System I (Promega). For the P2Y6 receptor, 40 PCR cycles were performed under the following conditions: 95°C for 30 s, 62°C for 1 min (annealing), and 72°C for 1 min (extension) for five cycles; 95°C for 30 s, 56°C for 1 min, and 72°C for 1 min for 34 cycles, with a last cycle with a 10-min extension stage. For GAPDH, only 30 cycles were performed, as follows: 95°C for 30 s, 55°C for 1 min, and 72°C for 1 min for 29 cycles, plus a last cycle with a 10-min extension stage.
The resulting PCR products were resolved on a 2% (wt/vol) agarose gel containing 10 µg/ml ethidium bromide and were observed under ultraviolet illumination. For the P2Y6 receptor, the nature of the PCR product (expected size, 339 bp) was confirmed by sequencing (Oswel DNA Sequencing Laboratories, Southampton, UK). In all experiments, the presence of possible contaminants was investigated using control RT-PCR assays of samples in which either mRNA had been excluded (blank) or reverse transcriptase had been omitted from the RT mixture.
Measurement of [Ca2+]i
[Ca2+]i was measured using previously described
methods (32). Each tubular
segment was loaded with fura2/acetoxymethyl ester (10 µM in microdissection
medium; Molecular Probes, Eugene, OR) for 1 h at room temperature and was
subsequently transferred to a superfusion chamber, where the ends of the
segment were aspirated into two glass holding pipettes (to prevent possible
perfusion of the luminal membrane). The segment was then superfused with HBSS,
at a rate of 10 ml/min, for a 5-min equilibration period. Fura2 fluorescence
was measured in a tubular portion of 20 to 30 cells, using a standard
photometric configuration (model MSP 21; Zeiss, Jena, Germany), during
superfusion with either HBSS alone or HBSS to which agonists had been added.
All solutions were stored in individual reservoirs at room temperature until
use; the temperature of each solution was increased to 37°C just before
introduction into the perfusion chamber.
After subtraction of tubular autofluorescence from the fura2 fluorescence intensities at 340 and 380 nm, [Ca2+]i was calculated using the equation presented by Grynkiewicz et al. (33), with a calcium dissociation constant for fura2 of 224 nM. The calibration parameters were determined from internal calibration assays using solutions containing 10 µM ionomycin and both 0 mM Ca2+ and 1 mM ethylene glycol bis(ß-aminoethyl ether)-N,N,N',N'-tetraacetic acid (for the minimal ratio) or 3 mM Ca2+ (for the maximal ratio).
Measurement of Phosphoinositide Metabolism
The method used was previously described in detail
(34,35).
Briefly, well preserved pieces of proximal tubules (i.e., a mixture
of S1, S2, and S3 cortical fragments) were sorted from tubule suspensions
prepared, by sieving, from non-collagenase-treated rat kidney cortex
(35). OMCD were microdissected
from collagenase-treated rat kidneys, as described above. All tubules were
labeled for 2 h in HBSS (2 mM Ca2+) containing 1 mCi/ml
myo-[3H]inositol (Amersham, Buckinghamshire, UK), in a
humid atmosphere at 37°C.
After labeling, segments were extensively rinsed at room temperature under stereomicroscopic observation, for removal of extracellular myo-[3H]inositol, and then batches of 10 segments (approximately 5-mm tubule length) were transferred, in 2 µl of HBSS, to glass test tubes containing 48 µl of HBSS (1 mM Ca2+). Incubations with agonists were initiated by the addition of 50 µl of HBSS (1 mM Ca2+) containing the agent (at double concentration) and LiCl (final concentration, 10 mM).
Reactions were terminated after 15 min by the addition of 940 µl of chloroform/methanol (1:2, vol/vol) and 200 µl of 5 mM Tris-ethylenediaminetetraacetate (pH 7.0). Water and chloroform (300 µl of each) were added to the reaction tube, which was then centrifuged for 5 min at 3000 x g at 4°C for separation of the phases. For each sample, the upper hydrophilic phase was removed for chromatography, whereas 500 µl of water and 500 µl of methanol were added to the remaining hydrophobic phase. After vortex-mixing and repeat centrifugation, the lower phase, containing phosphoinositides (PI), was recovered and evaporated to dryness in counting vials before measurement of radioactivity.
Radioactivities associated with free inositol, glycerophosphoinositol (GPI), and IP were separated by chromatography, as described previously (35). Samples were applied to columns containing 0.25 g of Dowex AG1-X8 resin, and free inositol, GPI, and IP were successively and respectively eluted with the following: (1) 3 mM Hepesbuffered water (pH 7.0), (2) 30 mM ammonium formate, and (3) 1 M ammonium formate and 0.1 M formic acid. The radioactivity contained in each eluate and in the PI extract was counted by ß-emission spectrometry, after the addition of 15 ml of Aquasol-2 scintillation cocktail (Packard Bioscience Ltd., Pangbourne, UK) to each vial. IP production was expressed as a percentage of the total radioactivity present in the sample (inositol plus GPI plus IP plus PI), because it was previously demonstrated that there is a good correlation between IP formation expressed in this way and that expressed per unit of tubule length (35,36).
Statistical Analyses
All data are presented as mean ± SEM. Statistical comparisons were
made using t tests for paired and unpaired samples and ANOVA, as
appropriate. Statistical significance was taken as P < 0.05.
Chemicals
UDP, ADP, and ATP (disodium salts), as well as arterenol bitartrate
(norepinephrine), carbamyl choline chloride (carbachol), angiotensin II, and
8-arginine vasopressin, were purchased from Sigma (Poole, Dorset, UK). Because
commercially available UDP contains as much as 10% UTP, the UDP stock solution
was treated for 1 h with hexokinase (10 U/ml), in the presence of 25 mM
glucose.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Effects of UDP on [Ca2+]i in Isolated Nephron
Segments
RT-PCR data indicated that P2Y6 receptor mRNA is present in
segments of the renal tubule, but they provide no information regarding
expression of the protein. In the absence of an antibody against the
P2Y6 receptor, we measured UDP-stimulated changes in
[Ca2+]i in most segments containing mRNA, i.e.,
the proximal tubule, the DTL, the MTAL, and the OMCD. As shown in
Figure 2A, significant
increases in [Ca2+]i occurred in the proximal tubule. In
contrast, the other segments were poorly responsive or unresponsive, although
they were sensitive to other PLC-stimulating agonists used as controls (ATP or
UTP for DTL and OMCD and angiotensin II for MTAL; results not shown). Compared
with the results we obtained previously with ATP and ADP
(23), the response to UDP in
the proximal tubule was characterized by more intra- and interanimal variation
(mean [Ca2+]i increase, 365 ± 40 nM; n =
33). Nine of 42 tubules were observed to be insensitive to UDP, although they
responded normally to either ATP (441 ± 74 nM, n = 4) or ADP
(460 ± 81 nM, n = 5). The effect of UDP dose-dependently
increased between 10 and 30 µM (Figure
2B). At all concentrations tested, the response was monophasic,
with a single sharp peak before [Ca2+]i returned to
resting values (Figure 2C). In
contrast, the responses to ATP and ADP were biphasic, consisting of a peak and
then a lower plateau phase that was sustained throughout exposure to the
agonist. Similarly, the responses to the other agonists used in this set of
experiments (carbachol and norepinephrine) were biphasic (Figures
2C,
3, and
4).
|
|
|
Because the proximal tubule segments used in these initial experiments were
microdissected at random from the kidney cortex and were not anatomically
localized, it was possible that the scatter of UDP-induced
[Ca2+]i changes was physiologic and reflected different
sensitivities of S1, S2, and S3 segments of the proximal tubule to this
nucleotide. Therefore, subsequent experiments were performed with localized
segments of proximal tubules. As stated in the Materials and Methods section,
S3 segments were identified by anatomic criteria that could not be applied to
S1 segments, because it is very difficult to microdissect proximal tubules
attached to glomeruli in non-collagenase-treated rat kidneys. As an
alternative, we used a functional criterion based on results from previous
studies, which demonstrated that changes in [Ca2+]i in
response to carbachol decrease from S1 to S3, whereas responses to
norepinephrine remain constant
(35). Therefore, responses to
UDP, carbachol, and norepinephrine were always measured in the same segments,
using carbachol as an index of localization and norepinephrine as an index of
tubule viability. Figure 3
presents sample traces obtained for the S1, S2, and S3 segments. The mean
UDP-induced responses were not statistically different between the S1 segment
(
[Ca2+]i = 340 ± 73 nM, n = 8)
and the S3 segment ([Ca2+]i = 425 ± 30 nM,
n = 10), a finding that suggests that the proximal tubule is
responsive to UDP along its entire length.
Finally, we observed that two consecutive responses to UDP (30 µM) did
not occur in the same proximal tubule, even when stimulations were separated
by 15 to 20 min of superfusion with control medium (data not shown). We took
advantage of this result to examine whether this desensitization was specific
for UDP or also applied to other nucleotides that had been previously
demonstrated to stimulate PLC in this tubule segment
(23). As illustrated by the
trace in Figure 4, previous
stimulation by UDP ([Ca2+]i = 374 ± 116
nM, n = 9) prevented the effect of a second basolateral application
of the nucleotide. However, these tubules remained sensitive to ADP
([Ca2+]i = 440 ± 118 nM, n = 6),
ATP ([Ca2+]i = 333 ± 89 nM, n =
3), and norepinephrine ([Ca2+]i = 404 ± 63
nM, n = 5), all of which were tested within the period of
desensitization to UDP.
Effects of UDP on PI Metabolism in the PCT
To confirm that the effects of UDP on [Ca2+]i were
mediated via G-protein-coupled receptor activation of the PLC pathway, we
assessed the effects of this agent on PI signaling in isolated segments of the
proximal tubule. Production of IP was also investigated in the OMCD, a segment
that expresses P2Y6 receptor mRNA
(Figure 1) but weakly responds
to basolateral UDP superfusion (Figure
2). As previously reported for the PCT
(35), approximately 80% of the
total radioactivity was incorporated as PI. In contrast, only 5% of the total
radioactivity appeared in the PI fraction in the OMCD, as reported for the
thick ascending limb of Henle's loop
(36).
For both segments, the percentages of radioactivity present in the IP pool under different experimental conditions are presented in Table 1. In the PCT, UDP (30 µM) typically caused a fivefold increase in IP production, compared with basal values (P < 0.01). This increase was slightly, but not significantly, larger than that evoked by either ATP (used at the same concentration) or norepinephrine. In the OMCD, the P2Y6 agonist also promoted a significant increase in the accumulation of IP (three- to fourfold, P < 0.05), as did ATP (sixfold, P < 0.01) and arginine vasopressin (sevenfold, P < 0.01).
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The P2Y6 receptor is functionally coupled to PLC, and receptor activation leads to transient increases in [Ca2+]i in several cell types (5,6,7). We used this coupling to examine the functional expression of renal P2Y6 receptors, by measuring changes in [Ca2+]i during the application of UDP to the basolateral membrane. In all segments of the proximal tubule (S1, S2, and S3), expression in the basolateral membrane was confirmed by the finding that peritubular UDP caused a dose-dependent increase in [Ca2+]i (Figures 2 and 3). This probably represents (at least in part) release of calcium from intracellular stores, because IP production was also stimulated by UDP (Table 1). Unlike the proximal tubule, more distal tubular segments that expressed P2Y6 receptor mRNA (Figure 1) did not respond to basolateral UDP superfusion with clear-cut increases in [Ca2+]i (Figure 2); these findings were noted for the DTL, the whole thick ascending limb, the CCD, the IMCD, and the OMCD. These data may indicate that the receptor is only weakly coupled to PLC in these segments or that it is expressed exclusively in the luminal membrane. In support of the latter possibility, several studies have established the presence of luminal P2Y6 receptors (12,13,15,22). However, our study did not allow us to address this question, because UDP had no access to the luminal membrane in our calcium experiments (see the Materials and Methods section). In contrast, the tubules used for the measurement of IP generation did have free open ends and were incubated for up to 15 min in the presence of UDP. Therefore, it is possible that the fourfold stimulation of IP production by UDP in the OMCD reflects activation of luminal receptors (Table 1), but contrary to this interpretation is the recent finding that UDP did not alter [Ca2+]i when applied to the lumen of microperfused mouse CCD (28). However, there are species differences in the distribution of other P2Y receptors along the nephron, as well as their cellular localization. For example, levels of functional expression of P2Y2 receptors in the basolateral membrane of the thick ascending limb are high in mice (25) but low in rats, despite the presence of mRNA (23), and evidence for luminal expression of P2Y2 receptors has been observed in mouse CCD but not in rabbits (28). Such species differences could also apply to the P2Y6 receptor, and the development of specific antibodies to the P2Y6 receptor would help address this issue.
Data in the literature have established that P2Y1 receptors (23,26) and, to a lesser extent, P2Y2 and/or P2Y4 receptors (23) are expressed in the basolateral membrane of rat proximal tubules. This raises the question of whether UDP responses actually reveal the presence of an additional P2 receptor (Y or X) or whether they result from interactions with other P2 receptor subtypes. Four pieces of evidence support UDP-induced [Ca2+]i changes as reliable indicators of the presence of the P2Y6 receptor. The first is that UDP exposure was associated with increased IP production, a finding that cannot be accounted for by UDP interactions with ionotropic P2X receptors. The second is that tubular segments that were previously demonstrated to express PLC-coupled P2Y2P2Y4 receptors (DTL and OMCD) and P2Y1 receptors (OMCD) in their basolateral membranes (23) were insensitive to UDP (Figure 1). The third is that the transient monophasic increases in [Ca2+]i elicited by UDP in proximal tubules are unlike the biphasic responses to other P2Y receptor agonists, such as ATP and ADP (Figures 2,3,4). This suggests that renal P2Y6 receptors may be coupled to different effector pathways, compared with P2Y1 and P2Y2 receptors. Indeed, a recent study reported that P2Y6 receptors expressed in Xenopus oocytes are coupled to only one class of G-protein, whereas P2Y2 receptors are coupled to two (37). There is also a large body of evidence indicating that different P2Y receptor subtypes expressed in the same cells activate different signal transduction pathways [see the report by Communi et al. (9)]. The fourth piece of evidence is our previous demonstration that no desensitization occurred when several successive stimulations with maximal concentrations of ATP and/or ADP were administered to proximal tubules (23). In contrast, in our present experiments we observed that a single UDP stimulation prevented further responses to this nucleotide but did not affect the ability of the proximal tubule to respond to ATP or ADP (Figure 4). Taken together, the data suggest that the response to UDP involves a receptor that is distinct from the ADP- and ATP-sensitive P2Y1 subtype.
We have not analyzed the mechanisms underlying the desensitization of the calcium response to UDP, i.e., whether it occurs at the receptor level or further along the PLC/[Ca2+]i pathway. Whatever the mechanism, this desensitization process, which seems to be specific for the P2Y6 receptor, may explain why the effects of UDP on [Ca2+]i were more variable in magnitude than were those of ATP and ADP (see the Results section). Little is presently known regarding the source and identity of the natural ligands for the P2Y6 receptor (1,9). It could be that abnormal nucleotide release, because of the conditions of the study animals and/or the tubule preparations, accounts for the variability in UDP-induced calcium effects; such variation in UDP effects has already been described for pancreatic duct cells (22). Preferential desensitization of P2Y6 receptor-induced responses, compared with P2Y2 receptor-induced calcium responses, has also been reported for nasal epithelium (13).
The maximal ATP-induced effects on IP production and [Ca2+]i were in the range of those induced by UDP or ADP alone, which may mean that the P2Y6 receptor is only weakly sensitive to ATP in rat proximal tubules, as it is when expressed in Xenopus oocytes (5) and other cell types (6,15,20,38). If this is true, then the effects of ATP must reflect mainly interactions with the basolateral P2Y1 receptor. Another possibility is that the P2Y6 and P2Y1 receptor subtypes are present in the same cells and hydrolyze the same pool of membrane PI and that a single stimulation of either one at high concentrations is sufficient to induce maximal effects on IP production and intracellular calcium release. These alternatives are not mutually exclusive, because we already have evidence for such a coupling between P2Y1 and P2Y2 receptors in the same cell type in the rat OMCD (23). If P2Y6, P2Y1, P2Y2, and/or P2Y4 receptors are coexpressed in the basolateral membrane of the same proximal tubule cells, then the important question is whether these nucleotides can induce similar or distinct physiologic responses (9). Perhaps there is some necessary functional overlap or redundancy. Published data from studies on the secretory epithelium of upper respiratory airways and exocrine glands indicate that different P2Y receptors coexpressed in the same cells all stimulated PLC and activated chloride currents (9). Results obtained in P2Y2 receptor-deficient mice indicate that the apical P2Y6 receptor can substitute for the inactivated P2Y2 receptor to regulate chloride secretion in the gallbladder (20). However, in addition to this common regulatory pathway, other data indicate that different (10,37) or the same (38) P2Y receptors can couple to different G-proteins in the same cell to activate different isoforms of PLC (39) and thus regulate different effectors (37,38). This may result in synergistic or opposing effects on cell functions. G-protein-dependent inhibition of calcium and potassium currents by P2Y6 receptors is thought to exert synergistic effects on neuronal excitability in rat sympathetic neurons. Conversely, ATP and ADP are known to induce opposite effects on platelet aggregation. From these observations, it is clear that the interactions among different P2Y receptors are specific for each cell type, depending on the nature of cellular components and on whether the receptor is targeted to the luminal or basolateral membrane.
|
Acknowledgments |
|---|
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
q/11 and to
PLC-ß3 via Gß
i3. J Biol Chem273
: 4695-4704,1998This article has been cited by other articles:
 |
|
 |
|
  V. Vallon P2 receptors in the regulation of renal transport mechanisms Am J Physiol Renal Physiol, January 1, 2008; 294(1): F10 - F27. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Guan, D. A. Osmond, and E. W. Inscho Purinoceptors in the Kidney Experimental Biology and Medicine, June 1, 2007; 232(6): 715 - 726. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. M. Turner, B. F. King, K. S. Srai, and R. J. Unwin Antagonism of endogenous putative P2Y receptors reduces the growth of MDCK-derived cysts cultured in vitro Am J Physiol Renal Physiol, January 1, 2007; 292(1): F15 - F25. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. G. Shirley, M. A. Bailey, and R. J. Unwin In vivo stimulation of apical P2 receptors in collecting ducts: evidence for inhibition of sodium reabsorption Am J Physiol Renal Physiol, June 1, 2005; 288(6): F1243 - F1248. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. A. Bailey Inhibition of bicarbonate reabsorption in the rat proximal tubule by activation of luminal P2Y1 receptors Am J Physiol Renal Physiol, October 1, 2004; 287(4): F789 - F796. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. J. Unwin, M. A. Bailey, and G. Burnstock Purinergic Signaling Along the Renal Tubule: The Current State of Play Physiology, December 1, 2003; 18(6): 237 - 241. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. S. Wildman, K. M. Hooper, C. M. Turner, J. S. K. Sham, E. G. Lakatta, B. F. King, R. J. Unwin, and M. Sutters The isolated polycystin-1 cytoplasmic COOH terminus prolongs ATP-stimulated Cl- conductance through increased Ca2+ entry Am J Physiol Renal Physiol, December 1, 2003; 285(6): F1168 - F1178. [Abstract] [Full Text]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
HOME
CURRENT ISSUE
ARCHIVES
JASN Express
ONLINE SUBMISSION
AUTHOR INFO
EDITORIAL BOARD SUBSCRIBE FEEDBACK ALERTS HELP |
