γ-MSH-like immunoreactivity in porcine pituitary and adrenal medulla. An immunochemical and immunocytochemical study

Abstract

A sensitive and specific radioimmunoassay for γ 2-melanotropin ( γ 2-MSH) has been developed that does not recognize α-, β-, γ 1- or γ 3-MSH. γ 2-MSH-like immunoreactivity could be demonstrated in the porcine pituitary and adrenal gland. The highest concentrations were detected in the neurointermediate lobe regardless of extraction procedure. The anterior lobe harboured lower concentrations and in adrenal gland extracts only small amounts were measured. Gel chromatography and high performance liquid chromatography of extracts of both pituitary and adrenal gland revealed several peaks of immunoreactive material, one of which eluted close to the position of synthetic γ 2-MSH. By immunocytochemistry γ 2-MSH immunoreactivity was localized to the adrenocorticotropin/α-MSH cells in the pituitary and to a subpopulation of the noradrenaline-storing cells in the adrenal medulla. Together, the immunocytochemical and immunochemical findings indicate the existence of γ 2-MSH-like material in the porcine pituitary and adrenal medulla.