Acute effects of recombinant murine leptin on rat pituitary-adrenocortical function

Leptin, the product of the ob gene, is an adipose-tissue secreted hormone, which regulates satiety, metabolic rate and thermogenesis. Many lines of evidence suggest the existence of mutual relationships between leptin and adrenal-cortex secretion, but in vivo studies gave rather conflicting results. Therefore, we have investigated the acute effect of the systemic bolus administration of leptin (5 or 10 nmol/kg) on the function of rat pituitary-adrenocortical function. The blood concentrations of ACTH, aldosterone and corticosterone were measured by specific RIA 60 or 120 min after the leptin injection. Leptin did not affect the blood concentrations of ACTH and aldosterone at 60 min, but at 120 min the lower dose of the peptide increased them. In contrast, the blood level of corticosterone was markedly enhanced by both doses of leptin at 60 and 120 min. Collectively, these findings indicate that leptin exerts a moderate acute activation of the pituitary-adrenocortical function in rats. They also suggest that the adrenocortical secretagogue action of leptin is not only mediated by the enhanced pituitary ACTH release, but is also consequent to a direct stimulatory effect of the peptide on adrenocortical cells.