Effect of leptin, insulin, and IGF-I on GnRH-induced LH secretion from porcine pituitary cells in vitro

The objective of this study was to analyse the response of porcine pituitary cells to leptin, insulin, and IGF-I in vitro. Pituitary cells were cultured in McCoy 5A medium without hormones (negative control), with GnRH (4x10⁻⁹M/L) (positive control), with GnRH and 10⁻¹¹-10⁻⁶ M/L of leptin, with GnRH and 3.9-91.0 mlU/L of insulin, or with GnRH and 1.03-39.2x10⁻⁹ M/L of IGF-I. After 6, 12, 18, 24, 30, and 36 h of cell incubation, the secretion of LH was determined. The obtained results showed that the effect of leptin and insulin on LH secretion from pituitary cells was dependent on the used dose of leptin. Leptin in concentrations 10⁻⁹, 10⁻⁸, and 10⁻⁷ M/L were significantly (P≤0.05) enhanced, whereas in concentration 10⁻⁶ M/L suppressed a LH secretion. Insulin at a dose from 3.9 to 13.0 mlU/L caused an increment, whereas in higher concentrations - a significant (P≤0.05) drop in LH secretion. Almost full positive correlation (r=0.98) between the level of IGF-I in the culture medium and LH secretion was found.