Apparent positive cooperativity in the mechanism of action of luteinizng hormone.

In vitro accumulation of cyclic AMP by rat Leydig cell preparation and mouse tumor Leydig cells in response to exogenous LH appears to display an apparent Hill coefficient of 2.5. This is suggestive of positive cooperativity at a level intermediate between binding and cyclic AMP production, although several alternative hypothesis cannot be excluded on the basis of these data alone. The Hill coefficient for testosterone is higher than unity, although it has not been established with adequate precision in these experiments.