The inhibitory actions of Pb on StAR protein expression and steroidogenic enzymes on steroidogenesis were analyzed by both linear and 2nd order polynomial models in MA-10 mouse Leydig tumor cells. Lead acetate, ranging from 10 -8 M to 10-5 M, caused inhibitory effects on StAR protein expression and steroidogenic enzymes. The correlation coefficients R2 (linear vs. 2nd order polynomial) were 0.93 vs. 0.96 for human chorionic gonadotropin-stimulated progesterone production, 0.38 vs. 0.79 for dibutyryl cAMP-stimulated progesterone production, 0.03 vs. 0.99 for the expression of StAR protein, 0.6 vs. 0.92 for P450 side-chain cleavage enzyme activity, and 0.52 vs. 0.96 for 3β-hydroxysteroid dehydrogenase activity. Thus, 2nd order polynomial model showed higher correlation coefficients than the linear model for predicting inhibitory actions of Pb on StAR protein expression and the activities of steroidogenic enzymes after exposure of Pb on steroidogenesis in MA-10 cells.
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