Metabolic responses of Sertoli cells in culture to various concentrations of follicle stimulating hormone and cholera toxin

The concentration of cholera toxin required for half-maximal stimulation of cAMP production by Sertoli cell enriched cultures (4.48 × 10−2 μg/ml) is greater than that required for half-maximal stimulation of 17β-estradiol synthesis from testosterone (2.34 × 10−4 μg/ml), [3H]thymidine incorporation into DNA (1.48 × 10−5μg/ml), or androgen binding protein production (2.43 × 10−6 μg/ml). The same relative dose response hierarchy was obtained with respect to stimulation of Sertoli cells with follicle stimulating hormone (FSH) preparations. Again, highest concentrations were required to elicit maximal cAMP production. The data are discussed in relation to an apparent paradox: If cAMP is the mediating 'second messenger' following stimulation by FSH or cholera toxin, why should highest concentrations of these agents be required to elicit 50% of maximal cAMP levels?