RELAXIN AND DECIDUALIZATION IN MICE - A REAPPRAISAL

The nature of the physiological stimulus inducing decidualization in t he endometrium is unknown. In this study we attempted to verify a rece nt report that relaxin can induce decidualization in intact mice prime d with a high dose of estradiol valerate (5 mu g) and a low dose (10 m u g) Of medroxyprogesterone acetate. In our study, neither s.c. nor in trauterine relaxin, nor intraluminal arachis oil, (an established deci duogenic stimulus) were able to induce decidualization. In addition, w hile oil was able to induce decidualization (increased uterine weight, and positive Pontamine Sky Blue and stromal alkaline phosphatase reac tions) in ovariectomized mice treated with a regimen of estradiol and medroxyprogesterone acetate designed to produce optimum uterine sensit ivity, no decidualization occurred in response to either s.c. or intra luminal relaxin. This study fails to provide any support for a role fo r relaxin as a deciduogenic stimulus.