The in vitro effect of leptin on basal and growth hormone-releasing hormone-stimulated growth hormone secretion from the ovine pituitary gland.

We have studied the direct effect of leptin on the secretion of GH from the anterior pituitary gland of the sheep. Using primary cultures of ovine pituitary cells, leptin (10(-9)-10(-7) M) treatment for 30 min did not affect basal or GHRH (10(-7) M)-stimulated GH secretion. Following treatment for 24 h, a dose of 10(-7) M leptin stimulated basal GH secretion. In contrast, doses of 10(-7) and 10(-8) M leptin inhibited GHRH-stimulated GH secretion after 24 h of treatment. These results suggest that leptin can have long-term effects on the somatotropes, but no acute effect. Furthermore, leptin appears to have opposite effects on basal and GHRH-stimulated GH secretion.