A transplantable rat leydig cell tumor—5. Cellular localization of beta-adrenergic and prostaglandin receptors and their effects on testosterone production

The cellular localization of β-adrenergic and prostaglandin (PG) receptors and their effects on adenylate cyclase activity (AC) and testosterone production in vitro were investigated in a transplantable rat Leydig cell tumor (H-540). Separation of the tumor cells in Percoll gradients revealed that the specific binding of [ 3H]PGE 1 and [ 125I]Cyanopindolol was found in the same fraction as that of [ 125I]LH. This fraction—judged by light microscopy of smears—consisted of tumor Leydig cells. In addition, [ 125H]cyanopindolol was found specifically bound in the red blood cell fraction. In the Leydig tumor cells, approx 25% of the β-adrenergic receptors was identified as β 1-receptors, whereas approx 75% of the receptors were of the β 2-subtype. The AC in Percoll purified Leydig tumor cells was stimulated by hCG (6-fold), PGE 1 (2-fold), PGE 2 (1.5-fold), PGI 1 (2-fold) and isoproterenol (2-fold). The AC in the red blood cell fraction was stimulated by isoproterenol whereas the PGs and hCG had little or no effect. hCG, isoproterenol and PGE 1 were able to stimulate testosterone production in vitro. At 44 h incubation, PGE 1 was the most potent stimulator of testosterone production. In conclusion, tumor Leydig cells possess hCG, PGE 1, PGI 2 and β-adrenergic receptors coupled to the AC. PGE 1 and β-adrenergic agonists stimulate testosterone production after prolonged incubation in vitro.