The role of protein kinase A and cyclin-dependent (CDC2) kinase in the control of basal and IGF-II-induced proliferation and secretory activity of chicken ovarian cells

Abstract

The aim of these experiments was to study the role of protein kinase A (PKA), cyclin-dependent kinase 2 (CDC2) and insulin-like growth factor II (IGF-II) in the control of ovarian function in domestic fowl, as well as the role of PKA and CDC2 in mediating the effects of IGF-II on the ovary. For this purpose, we studied the influence of an inhibitor of PKA (KT5720; 50 ng/ml), a CDC2 blocker (olomoucine; 1 μg/ml), IGF-II (0, 1, 10 or 100 ng/ml) and their combinations on cultured fragments of chicken ovarian follicular wall. Accumulation of PKA and CDC2 and secretion of progesterone (P 4), testosterone (T), estradiol (E 2) and arginine–vasotocin (AVT) were evaluated by using SDS-PAGE–Western blotting and RIA/EIA. IGF-II addition to culture medium stimulated T, E 2 and AVT secretion and inhibited P 4 secretion. These changes were associated with an increase in PKA and a decrease in CDC2 accumulation. The PKA blocker KT5720, when given alone, increased accumulation of PKA and secretion of T and E 2, but not AVT and inhibited P 4 secretion. The PKA blocker also prevented and even reversed the effects of IGF-II on PKA and steroid hormones secretion, but enhanced the action of IGF-II on AVT. The inhibitor of CDC2, olomoucine, when given alone, suppressed the expression of CDC2 and the secretion of P 4 and AVT (but not T and E 2). When given together with IGF-II, it augmented IGF-II-induced suppression of CDC2 and reversed the effects of IGF-II on P 4 (but not on T, E 2 or AVT). These observations demonstrate the involvement of PKA, CDC2 and IGF-II in regulating the secretory activity of avian ovarian cells. Our data also suggest the involvement of PKA in the mediation of IGF-II effects on P 4, T, E 2 and AVT secretion. CDC2 can mediate the effects of IGF-II on ovarian P 4 secretion but not on other hormones.