Gamma 2-MSH immunoreactivity in the human heart

In patients undergoing aorto-coronary by-pass surgery, we found a 26% arterial-venous difference of immunoreactive gamma 2-melanocytostimulating hormone (MSH), a proopiomelanocortin (POMC) derived peptide known to possess profound hemodynamic effects. These results prompted an investigation of the presence of gamma 2-MSH in the human heart. Using a two-step extraction procedure, regions of human hearts were examined by sensitive and specific radioimmunoassays to determine their gamma 2-MSH content. Mean (+/- SEM) concentrations of 0.14 +/- 0.023 pmol/g and 0.12 +/- 0.017 were found in right atrium and right ventricle, respectively. High performance liquid chromatography indicated that 80-90% of the total immunoreactivity eluted in a single sharp peak in a position identical to that of synthetic gamma 2-MSH.