Isolation of highly purified Leydig cells by density gradient centrifugation

Purification of specific endocrine cells from mixed populations after dispersion of target tissues is important for detailed analysis of mechanisms of hormone action. A simple method for rapid isolation of endocrine cells with retention of biological integrity, has been developed by centrifugation in density gradients formed with Metrizamide. By this procedure, highly purified Leydig cells retaining morphological and biochemical characteristics were obtained. Such preparations bound 20, 300+/-3, 100 molecules of hCG per cell with affinity of 1.1+/-0.25 X 10(10) M-1. During incubation with hCG, cyclic AMP and testosterone responses of purified Leydig cells were considerably increased, and hCG concentrations as low as 0.2 pM caused activation of cAMP-dependent protein kinase.