Regulation of Prostaglandin Endoperoxide Synthase by Cyclic Adenosine 3′,5′-Monophosphate in the in Vitro-Perfused Rat Ovary1
Mats Brännström, Lasse Larson, Barbro Basta, Lars Hedin
1989
Biology of Reproduction
The preovula:ory regulation of two enzymes in the prostaglandin biosynthetic pathway, prostaglandin endoperoxide synthase (PGS) and prostacyclin synthase (ISN), was examined in granulosa cells and residual tissue of rat ovaries perfused in vitro. Ovaries from rats primed with pregnant mare's serum gonadorropin (20 IU) were perfused for up to 20 h starting the morning of induced proestrus. The amounts of PGS and ISN present were analyzed with immunobloning techniques. Soluble extracts from
more »
... osa cells and residual ovarian tissues were obtained at different times (0 h, 3 h, 7 h, 12 h) after treatment in vitro with luteinizing hor,none (LII, 0.1 g.tgl ml) and 3-isoburyl-1-methylxanthine (!BMX; 0.2 mM) and a: 7 h in untreated control ovaries or after treatment with forskolin (30 lAM) or LII (0.1 tgIml). The levels in the perfusion medium of cyclic adenosine 3', 5'-monophosphate (cAMP), progesterone, testosterone, and estradiol were measured and the number of ovulations were examined. The levels of PGS after treatment with LII + JBMX increased up 1o7 hand remained high at 12 h, a time that is close to the rime of ovulation. The increase was more pronounced in the granulosa cells than in the residual tissue. Treatment with forsko!in induced synthesis of PGS in granulosa cells, and the levels at 7 h were similar to those after stimulation with LII + JBMX. The levels of PGS were lower in granulosa cells of the group stimulated with LII alone than in granulosa cells from ovaries stimulated with LII + IBMX orforskolin. There were significantly (p<O.O1) more ovulations in the groups treated with LII + IBMX (242 ± 5.1) orforskolin (212 ± 4.8) than in the group treated with LII alone (3.8 ± 1.4). The release of cAMP was greatest in the group treated with forskolin, followed by the group treated with LII + IBMX and the group treated with LII alone. Progesterone remained highest in the forskolin-ereared group,followed by the group treated with LII + !BMX and LII alone. The levels of testosterone and estradiol were similar in all treatment groups. In conclusion, the induction of PGS but not of ISN was stimulated by LII and mediated by cAMP. Moreover, the total ovarian levels of PGS were related to the nwnber of ovulating follicles, unplying that a rise in PGS levels is one mechanism by which the ovulatory rise infollicularprostaglandin levels is mediated.
doi:10.1095/biolreprod41.3.513
pmid:2480162
fatcat:yljevrt7gnblbnzsygpcvh6hzq