Influence of acidosis on noradrenaline-induced vasoconstriction in adipose tissue and skeletal muscle.

Vasoconstriction due to parallel i.a. injections of NA were studied in subcutaneous adipose tissue and gracilis muscle preparations in dogs. The vasoconstrictor response to NA was significantly lower in adipose tissue than in muscle. Only in muscle did acidosis inhibit NA-induced vasoconstriction. The beta-receptor antagonist propranolol increased the vasoconstrictor response in adipose tissue to the level of skeletal muscle. The lack of significant inhibition of NA-induced vasoconstriction in adipose tissue may be due to the simultaneous inhibition of two opposing mechanisms-alpha-adrenergic vasoconstriction and beta-adrenergic vasodilatation. After propranolol acidosis inhibited NA-induced vasoconstriction equally in adipose tissue and muscle. The difference between adipose tissue and muscle may thus be due to a greater importance of a beta-adrenergic vasodilator mechanism in the former tissue. The metabolic response to isoprenaline was inhibited by acidosis, while the direct vasodilatation was unaffected. It is suggested that the beta-adrenergic vasodilator mechanism that is inhibited by acidosis is related to the metabolism of the tissue.