Evidence for local relaxin ligand-receptor expression and function in arteries.

Relaxin is a 6 kDa protein hormone produced by the corpus luteum and secreted into the blood during pregnancy in rodents and humans. Growing evidence indicates that circulating relaxin causes vasodilatation and increases in arterial compliance, which may be among its most important actions during pregnancy. Here we investigated whether there is local expression and function of relaxin and relaxin receptor in arteries of nonpregnant females and males. Relaxin-1 and its major receptor, Lgr7, mRNA are expressed in thoracic aortas, small renal and mesenteric arteries from mice and rats of both sexes, as well as in small renal arteries from female tammar wallabies (an Australian marsupial). Using available antibodies for rat and mouse Lgr7 receptor and rat relaxin, we also identified protein expression in arteries. Small renal arteries isolated from relaxin-1 gene-deficient mice demonstrate enhanced myogenic reactivity and decreased passive compliance relative to wild-type (WT) and heterozygous mice. Taken together, these findings reveal an arterial-derived, relaxin ligand-receptor system that acts locally to regulate arterial function.