Progesterone production in bovine luteal cells treated with drugs that modulate nitric oxide production

The aim of this study was to investigate the influence of nitric oxide (NO) donors (S-nitroso-L-acetyl penicillamine, spermine-NO complex and sodium nitroprusside) and NO synthase inhibitors (N(omega)-nitro-L-arginine methyl ester, N(omega)-nitro-l-arginine, and (+/-)-2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine) on progesterone production by dispersed bovine luteal cells cultured for 24 h. All NO donors inhibited progesterone production and increased nitrite or nitrate concentration in the medium in a dose-dependent manner. Secretion of progesterone was reduced to 75% (P < 0.01), 56% (P < 0.001) and 37% (P < 0.001) by S-nitroso-L-acetyl penicillamine; to 65% (P < 0.001), 45% (P < 0.001) and 33% (P < 0.001) by spermine-NO complex and to 77% (P < 0.05), 74% (P < 0.01) and 54% (P < 0.001) by sodium nitroprusside treatments at concentrations of 10(-5), 10(-4) and 10(-3) mol l(-1), respectively, compared with the concentration of this hormone measured in cells cultured in medium alone. NO synthase inhibitors decreased significantly (P < 0.05) nitrite or nitrate concentration and increased progesterone secretion with different potency at different doses. Significant increases in progesterone production were observed after N(omega)-nitro-L-arginine methyl ester treatment at a concentration of 10(-5) mol l(-1) and 10(-4) mol l(-1), and after N(omega)-nitro-l-arginine administration at a concentration of 10(-6) mol l(-1) (P < 0.01) and 10(-5) mol l(-1) (P < 0.05), compared with the concentration of this hormone measured in control cells. The results indicate that both NO donors and NO synthase inhibitors regulate steroidogenesis in cultured bovine luteal cells from days 10 to 14 of the oestrous cycle; however, the degree of progesterone inhibition by NO donors and stimulation by NO synthase inhibitors was dependent on the drug used.