γ ₂‐MSH increases during graded exercise in healthy subjects: comparison with plasma catecholamines, neuropeptides, aldosterone and renin activity

Summary. To evaluate the possibility that the proopiomelanocortin (POMC)‐derived peptide γ₂‐melanocyte stimulating hormone (γ₂‐MSH) has a role in circulatory regulation in man we studied circulating levels of this peptide at three different stages of physical activity in 10 young healthy subjects. The results were compared to simultaneously measured plasma levels of catecholamines, neuropeptide Y, vasopressin, renin activity, aldosterone and human α‐atrial natriuretic peptide (α‐hANP) and of the vasodilatory peptides calcitonin gene‐related peptide, substance P and vasoactive intestinal peptide. The plasma levels of γ₂‐MSH‐LI (like immunoreactivity) increased from 1009 ± 101 pmol 1^‐1 at supine rest to 1281 ± 79 pmol 1^‐1 when measured after 10 min walking (P<0·05), and remained at this increased level also after a consecutive further increase of physical activity (4 min stair rush), 1293 ± 87 pmol 1^‐1 (P<0·05 vs. at rest). The increase in circulating γ₂‐MSH‐LI levels preceded the elevation of the venous plasma noradrenaline level, but did not rise further with more pronounced activation of the sympathetic nervous system at the highest grade of physical activity examined.