The Effect of Interleukin-2 on the Release of Gonadotropin and Prolactin in Vivo and in Vitro.

: To evaluate a possible physiological role of Interleukin-2 (IL-2) in the control of Luteinizing hormone (LH), Follicle stimulating hormone (FSH) and Prolactin (PRL) release, conscious, ovariectomized (OVX) rats were given injections of IL-2 into the third ventricle. The third ventricular injection of IL-2 induced a significant decrease in plasma LH levels when compared to values in control animals (P < 0.05). Plasma LH concentrations were significantly decreased within 5 min after the injection of IL-2 and remained decreased for 1 h. In contrast, injections of IL-2 had no effect on plasma FSH or PRL levels. To evaluate a possible direct action of IL-2 on LH, FSH and PRL release from the anterior pituitary gland, the cytokine was incubated with dispersed anterior pituitary cells for 4 h. IL-2 in the dose range between 10(-1) and 10(-3) unit stimulated the release of LH and FSH into the culture medium (P < 0.05, P < 0.025 vs. control, respectively). The release of PRL from incubated anterior pituitary cells was not affected at any dose of IL-2 tested. These results indicate that IL-2 possibly plays an inhibitory role in the control of gonadotropin secretion, via hypothalamic action, although it acts directly to stimulate the release of the gonadotropins at the level of the anterior pituitary gland.