The (+)- and (-)-gossypols potently inhibit human and rat 11β-hydroxysteroid dehydrogenase type 2

Gossypol has been proven to be a very effective male contraceptive. However, clinical trials showed that the major side effect of gossypol was hypokalemia. Gossypol occurs naturally as enantiomeric mixtures of (+)-gossypol and (-)-gossypol. The (-)-gossypol is found to be the active component of antifertility. 11 beta-Hydroxysteroid dehydrogenase 2 (11 beta HSD2) has been demonstrated to be a mineralocorticoid receptor (MR) protector by inactivating active glucocorticoids including corticosterone (CORT) in rats, and therefore mutation or suppression of 11 beta HSD2 causes hypokalemia and hypertension. In the present study, the potency of gossypol enantiomers was tested for the inhibition of 11 beta HSD1 and 2 in rat and human. Both (+) and (-)-gossypols showed a potent inhibition of 11 beta HSD2 with the half maximal inhibitory concentration (IC50) of 0.61 and 1.33 mu M for (+) and (-)-gossypols, respectively in rats and 1.05 and 1.90 mu M for (+) and (-)-gossypols, respectively in human. The potency of gossypol to inhibit 11 beta HSD1 was far less; the IC50 was >= 100 mu M for racemic gossypol. The gossypol-induced hypokalemia is likely associated with its potent inhibition of kidney 11 beta HSD2. (C) 2009 Elsevier Ltd. All rights reserved.