CENTRAL HEMODYNAMIC-EFFECTS OF RECOMBINANT HUMAN RELAXIN IN THE ISOLATED, PERFUSED RAT-HEART MODEL

Objective: To determine the cardiac effects of relaxin in the isolated , perfused rat heart model, and to see if pregnancy modifies the hormo ne's actions. Methods: Hearts were excised from 18 female Sprague-Dawl ey rats (ten pregnant, eight nonpregnant) and attached to a Langendorf f apparatus. Left ventricular systolic pressure, heart rate, and contr actility were measured. Hearts were exposed serially to 0.5, 1.0, 2.0, 4.0, 8.0, and 16.0 ng/mL concentrations of recombinant human relaxin. Results: Hearts from pregnant rats had lower heart rates than those f rom nonpregnant animals. Relaxin increased heart rate, left ventricula r systolic pressure, and contractility in a dose-dependent fashion. Pr egnancy did not modify this response. Conclusion: Recombinant human re laxin is a potent inotropic and chronotropic agent. The effects couple d with the physiologic increase of relaxin during human pregnancy indi cate that relaxin may be involved in the cardiovascular changes of pre gnancy.