Received September 13, 2005
Accepted on September 3, 2006

CLINICAL SCIENCE: Hemodynamics and Vascular Regulation

Influence of Recombinant Human Relaxin on Renal Hemodynamics in Healthy Volunteers

Marie C. Smith ^*1, Lee A. Danielson , Kirk P. Conrad ^Dagger;, and John M. Davison ^*

*School of Surgical and Reproductive Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom; Department of Pathology, University of New Mexico School of Medicine, Albuquerque, New Mexico; and Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, Florida

¹ To whom correspondence should be addressed. E-mail: m.c.smith{at}ncl.ac.uk.

	Abstract

Maternal renal hemodynamic adaptation to human pregnancy is one of the most dramatic of all physiologic changes, but the factors that are responsible have remained elusive. In rat pregnancy, there are comparable renal hemodynamic changes, and in this species there is comprehensive evidence that the ovarian hormone relaxin (RLX) is responsible. This study investigated the renal effects of recombinant human RLX (rhRLX) in humans. Eleven volunteers (six male, five female) received intravenous infusions of rhRLX over 5 h at an infusion rate that was chosen to sustain serum concentrations that are comparable to early pregnancy. The renal clearances of inulin and para-aminohippurate were used to measure GFR and renal plasma flow, respectively. Irrespective of gender, renal plasma flow was increased by 47% compared with baseline levels (P < 0.0001), but no significant change was observed in GFR. There were no side effects or adverse reactions of rhRLX given as an intravenous infusion, and the data suggest that RLX indeed may be one of the elusive renal vasodilatory factors in human pregnancy. Further work is necessary to elucidate the complimentary factors that permit the concomitant increase in GFR during pregnancy.