Abstract. Relaxin (Rlx) classically causes uterine quiescence during pregnancy and cervical dilatation prior to parturition. Its actions involve major changes in the components of the extracellular matrix of these tissues. The activities of three enzymes, collagenase, proteoglycanase and β-glucuronidase, major determinants of the integrity of the extracellular matrix have been measured in the rat uterus and cervix in different reproductive states. The results show that there are marked differences in the changes of these enzymes occurring in the uterus and cervix during the course of pregnancy and the puerperium. It was not possible to directly relate these changes to a single hormonal event over this period of major endocrine fluctuations. Two models have therefore been used in an attempt to delineate the effects of oestrogen and Rlx on the tissue enzyme levels or their secretion into culture medium. In the first model cyclic animals were treated with oestrogen alone or oestrogen followed by Rlx and tissue enzyme levels measured. The addition of Rlx treatment reversed an inhibiting effect of oestrogen alone on both uterine and cervical collagenase and proteoglycanase activities, at the same time as completely obliterating the stimulating effect of oestrogen on uterine and cervical β-glucuronidase activity. A second model used in vivo oestrogen priming of cyclic rats followed by in vitro Rlx treatment and measurement of the enzymes secreted into the culture medium over 7 days. The results showed as in the first model that Rlx treatment could in particular overcome the inhibiting effect of oestrogen on uterine proteoglycanase secretion without affecting β-glucuronidase levels. In contrast, the effect of Rlx on the cervix was to decrease collagenase and proteoglycanase secretion whilst not affecting the β-glucuronidase levels.
Pregnancy-induced changes in substance P and neurokinin 1 receptor (NK1-R) expression in the rat uterus
