NO EFFECTS OF HUMAN RELAXIN ON THE ACTIVE AND PASSIVE BIOMECHANICAL PROPERTIES OF ISOLATED CERVICAL SPECIMENS FROM NONPREGNANT WOMEN

Objective: To evaluate the effect of human relaxin (hRLX-2) on the act ive and passive biomechanical properties of cervical tissue in vitro. Material: Cervical samples were obtained from the middle part of the c ervix in 22 nonpregnant women undergoing hysterectomy. Methods: The ef fect of hRLX-2 (10(-7) M) on the active biomechanical properties was s tudied on vasopressin (10(-8) M) induced smooth muscle contractions in an organ bath model. The effect on the passive biomechanical properti es were studied after incubation of the strips for 48 h with hRLX-2 (1 0(-8) M and 10(-9) M). Subsequently, the specimens were stretched in a material testing machine until they broke. The load applied and the e longation were simultaneously recorded and the results translated into stress-strain curves. Results: hRLX-2 did not influence the vasopress in-induced contractility of cervical strips from nonpregnant women in this study. No synergistic effect of progesterone could be demonstrate d. The passive biomechanical properties (tensile strength, extensibili ty, stiffness or failure energy) did not change significantly after re laxin incubation. The results obtained in vitro do not suggest an impo rtant physiological effect of relaxin on the human nonpregnant cervix. (C) 1997 Elsevier Science B.V.