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. 2001 Jun;107(11):1469-75.
doi: 10.1172/JCI11975.

Relaxin is essential for renal vasodilation during pregnancy in conscious rats

J Novak  1 , L A Danielson, L J Kerchner, O D Sherwood, R J Ramirez, P A Moalli, K P Conrad
Affiliations

Relaxin is essential for renal vasodilation during pregnancy in conscious rats

J Novak et al. J Clin Invest. 2001 Jun.

Abstract

Marked vasodilation in the kidney and other nonreproductive organs is one of the earliest maternal adaptations to occur during pregnancy. Despite the recognition of this extraordinary physiology for over four decades, the gestational hormone responsible has remained elusive. Here we demonstrate a key role for relaxin, a member of the IGF family that is secreted by the corpus luteum in humans and rodents. Using a gravid rodent model, we employ two approaches to eliminate relaxin or its biological activity from the circulation: ovariectomy and administration of neutralizing antibodies. Both abrogate the gestational elevation in renal perfusion and glomerular filtration, as well as preventing the reduction in myogenic reactivity of isolated, small renal arteries. Osmoregulatory changes, another pregnancy adaptation, are also abolished. Our results indicate that relaxin mediates the renal vasodilatory responses to pregnancy and thus may be important for maternal and fetal health. They also raise the likelihood of a role for relaxin in other cardiovascular changes of pregnancy, and they suggest that, like estrogen, relaxin should be considered a regulator of cardiovascular function.

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Figures

Figure 1
Figure 1
Renal function in conscious virgin and day 11 pregnant rats treated with rat relaxin-neutralizing antibody (MCA1) or control antibody (MCAF). (a) GFR. (b) ERPF. (c) ERVR. (d) MAP. AP < 0.01 vs. other groups; BP < 0.05 vs. MCA1 and MCAF virgin.
Figure 2
Figure 2
Renal function in conscious virgin and day 14 pregnant rats treated with rat relaxin-neutralizing antibody (MCA1) or control antibody (MCAF). (a) GFR. (b) ERPF. (c) ERVR. (d) MAP. AP < 0.01 vs. other groups; BP ≤ 0.05 vs. MCA1 and MCAF pregnant.
Figure 3
Figure 3
Myogenic reactivity of small renal arteries. (a) Virgin and day 12 to 14 pregnant rats treated with rat relaxin-neutralizing antibody (MCA1) or control antibody (MCAF). (b) Pregnant rats were either ovariectomized (Ovex) on gestational day 8 and replaced with 17β-estradiol (E2) and progesterone (P) or sham-ovariectomized. AP < 0.01 vs. other group(s).
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