THE INFLUENCE OF THE OVARIAN HORMONES ON THE ACTOMYOSIN CONTENT AND THE DEVELOPMENT OF TENSION IN UTERINE MUSCLE

Abstract

Actomyosin concentrations and tensions were measured in the rabbit uterus during pregnancy and in ovariectomized hormone-treated animals. The results showed that actomyosin concentration and tension in g./mm.² longitudinal muscle followed similar courses during pregnancy. This was not so in the hormone-treated animals. Small quantities of oestrogen were sufficient in ovariectomized animals to produce a major difference between the untreated and treated animals. With higher doses only the concentration of the actomyosin increased linearly. During pregnancy a significant correlation was found between the number of foetuses in each horn, the quantity of actomyosin and the weight of the horn. The major increase in tension and actomyosin concentration occurred in the last half of pregnancy when the increase in uterine volume accelerates. The importance of this growth, as opposed to hormonal environment, was further emphasized by experiments in unilaterally pregnant rabbits in which both these quantities were significantly greater in the parous horn than in the non-parous horn. The effects of progesterone were also investigated.