Reports have indicated that a new class of POMC peptides, the gamma (delta) MSH's play a role in cardiovascular, renal and adrenal regulation. Of these peptides, gamma-l and gamma-2-MSH appear to have central sympathetic nervous system-mediated pressor and cardioaccelerator effects. These actions may therefore qualify these peptides as potential candidates as hypertension-promoting agents. Studies by Pedersen and Brownie (1983) have demonstrated high specific binding of gamma-3-MSH in several tissue types including adipose, skeletal muscle, testis, adrenal, cardiac muscle, ovary and spleen. However, little or no binding was observed in kidney tissue. Gamma-3-MSH possess structural similarities with gamma-l and gamma 2-MSH, however, gamma-3-MSH does nor possess pressor activity. The hypothesis for these study is that there are specific gamma-l-MSH receptors which regulate renal and cardiovascular function by activation of the central sympathetic nervous system, and possibly direct effects on the kidney and adrenal. The initial aim in this study is to identify gamma-l-MSH receptors in regions of the brain (i.e., midbrain, hindbrain and cortex), the cortical and medullary regions of the kidney, and the adrenal. Following this observation, our next objective we will be to biochemically and morphologically localize the gamma-l-MSH receptors in more specific structures of the brain (i.e., the antero-ventral 3rd ventricle regions structures, the area postremia of the hindbrain, brain cortex, as well as regions of the kidney and adrenal. Once these specific receptors have been identified and localized, we will then examine how receptor populations vary in an experimental model of hypertension. The results from these studies may help in defining a role for gamma-MSH peptides in renal and cardiovascular physiology.
