Galanin stimulates steroidogenesis in rat Leydig cells

The present study was designed to evaluate whether galanin could play a role in the regulation of testicular steroidogenesis. To this purpose, using purified rat Leydig cells, we examined the effects of galanin on basal and hCG- or LHRH-induced testosterone production and the interference of a specific galanin receptor antagonist, galantide, on galanin activity. Moreover, since it has been shown that galanin-induced stimulation of LHRH secretion appears to involve the release of prostaglandin E2 (PGE2) as intracellular mediator, we evaluated also the effect of galanin on Leydig cells PGE2 output and the interference of indomethacin, a cycloxygenase blocker, on its activity. Furthermore, the effect of nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, was also examined. Data obtained indicate that galanin amplified testosterone response to hCG or LHRH whilst galantide prevented its potentiating activity. Moreover, galanin stimulated PGE2 output though this fatty acid is not involved in galanin activity on Leydig cells as indomethacin failed to affect its amplification of testosterone production. The possible involvement of leukotrienes should also be excluded as NDGA did not modify galanin action. In summary, the present study indicates that galanin potentiates acute gonadotropin or LHRH steroidogenic action on Leydig cells and that this activity is specific and receptor-mediated as it is prevented by a specific receptor antagonist.