Regulation of adenosine 3',5'-cyclic monophosphate (cAMP)-binding proteins by 17 beta-estradiol and N6,O2'-dibutyryl cAMP (DBcAMP) in rat anterior pituitary cells.

Abstract

The studies in this report were designed I) to characterize the changes in cAMP-binding proteins in the rat anterior pituitary (AP) during the estrous cycle and with aging; 2) to determine whether the increase in cAMP-binding activities by 1 711-estradiol (E2) can be mimicked by N6 ,o� ‘-dibutyryl adenosine 3’,5’-cyclic monophosphate (DScAMP). In 4-month-old cycling female rats, the specific cAMP-binding activity per AP was lowest at diestrus, significantly increased at estrus, and maximum at metestrus (3.40 ± 0.37 pmol/AP, or 148% of the level at diestrus). The specific cAMP-binding activity per mg protein was also greatest at metestrus (11.02 ± 0.87 pmoll mg protein), but lowest at proestrus (6.82 ± 0.08 pmol/mg protein). The rise in serum E2 levels in proestrus preceded the rise in pituitary cAMP-binding activity in estrus and metestrus. With aging, the specific cAMPbinding activity at estrus decreased from 2.88 ± 0.09 pmol/AP at 4 months to 2.33 ± 0.02 pmol/AP at 12 months or to 2.19 ± 0.04 pmol/AP at 24 months. The cAMP-binding activity of a pituitary culture system was increased by treatment with either E2 (1 nM) for 6 days or DBcAMP (1 mM) for 18 h to 140% and 130%, respectively, of that in nontreated controls. Since we reported earlier that E2 stimulates both cAMP levels and cAMP binding in the pituitary and our present data indicate that cAMP can mimic E2 stimulation of cAMP binding, it is likely that E2 regulates pituitary cAMP-binding via an effect on cAMP production.