Abstract
The calmodulin levels of human and rat myometrium were measured during pregnancy and under estrogen, progesterone administration, and uterine muscle contraction at the same time was also measured. The calmodulin concentration in the uterine muscle was increased as the stage of pregnancy advanced. This increase also intensified. the maximum contractility of the uterine muscle together with the increase of growth during pregnancy. The calmodulin levels were increased by the administration of estrogen and this increase was restricted by progesterone. As a result, the adjustment of the calmodulin level by administration of these steroid hormones was found to be a very interesting mechanism for studying the physiology of uterine muscle contractions.
