Progesterone production by binucleate trophoblastic cells of cows

Incubation of 1 x 10(6) bovine binucleate trophoblastic cells (BTC) for 6 h with 0.20 and 0.30 microM-Ca2+ ionophore A23187 increased (P less than 0.01) net progesterone production 49% and 111%, respectively, compared to BTC without A23187. Addition of 3 mM-8-bromo-cAMP with A23187 had no effect on the response. Trifluoperazine (40 microM), an inhibitor of calmodulin, and ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (1.0 mM), a Ca2+ chelator, decreased (P less than 0.01) progesterone production. Progesterone production by BTC incubated for 6 h with fetal bovine serum or lipoprotein-deficient serum (LPDS) did not differ. Addition of bovine serum low-density lipoprotein or high-density lipoprotein to LPDS did not affect progesterone production. Aminoglutethimide (100 microM) decreased (P less than 0.01) progesterone production by BTC. These results indicate that progesterone production by bovine BTC is Ca2+-dependent, cyclic nucleotide-independent, and not stimulated by bovine serum lipoproteins.