Biology of Reproduction, Vol 31, 742-751, Copyright © 1984 by Society for the Study of Reproduction

ARTICLES

Uterine adenylate cyclase activity during the estrous cycle and early progestation in the rat: responses to fluoride activation and decidual induction

AM Bekairi, RB Sanders and JM Yochim

Uterine adenylate cyclase (AC) activity of the rat was measured by radiochemical analysis during the estrous cycle and early pseudopregnancy. During the estrous cycle, AC activity increased from 4.6 to 16.9 pmol cAMP formed/min X mg protein between metestrus and proestrus. Although AC was activated 2- to 3-fold at all cycle stages by 10 mM NaF, the resulting pattern of activity was similar to that measured in the absence of fluoride. The results demonstrated that the pattern of AC activity during the cycle was similar to that of other estrogen-sensitive uterine enzymes and that the ovarian hormones probably altered enzyme biosynthesis and turnover to a greater extent than activation and kinetic properties. Following the induction of pseudopregnancy by cervical stimulation, enzymic activity increased from 3.5 to 9.4 pmol between Days 1-4 (Day 1=leukocytic vaginal smear) and declined thereafter. AC activity was increased 2- to 5-fold by NaF on all days. AC activity was similarly increased by a mechanical trauma to the uterus, but only when the trauma was applied on Day 4. Following trauma to the uterus, AC activity was not increased further by NaF. The similarities between the physicochemical characteristics of AC during the estrous cycle and early progestation suggested that the enzyme during all endocrine states had virtually identical properties. However, the transient sensitivity to activation after trauma on Day 4 was unique to progestational uteri. Because the properties of enzyme were not altered by the endocrine state of the tissue, the transient sensitivity to activation by trauma was suggested to be a result of hormone-induced alterations in the membrane in which AC is sequestered.