The effect of calcium ions on testosterone production in Leydig cells from rat testis

Leydig-cell suspensions, prepared from rat testes, were incubated with different amounts of Ca²⁺ with and without added luteinizing hormone. The basal testosterone production in the absence of luteinizing hormone was unaffected by the Ca²⁺ concentration in the incubation medium. The luteinizing hormone-stimulated testosterone production, however, was progressively decreased in the absence of Ca²⁺ to one-third of that with 2.50 mM-Ca²⁺. This decrease in luteinizing hormone-stimulated testosterone production was independent of the different concentrations of luteinizing hormone (0-10μg/ml) used and could be restored by the addition of Ca²⁺ to the incubation medium. The restoration of the stimulation was achieved within 30 min after the addition of Ca²⁺ to the medium. Activation of cyclic AMP-dependent protein kinase by luteinizing hormone was not decreased by omission of Ca²⁺ from the incubation medium, suggesting that Ca²⁺ may be involved in steroidogenesis at a stage beyond the luteinizing hormone receptor-adenylate cyclase-protein kinase system.