Beta-3 adrenergic agonist, BRL-26830A, and alpha/beta blocker, arotinolol, markedly increase regional blood flow in the brown adipose tissue in anesthetized rats.

Abstract

Regional vascular effects of some adrenergic agents, focussing on brown adipose tissue (BAT), were investigated using tracer microspheres with a reference sample method in the anesthetized rat. Intravenous injections of 0.5 mg/kg BRL-26830A, a beta 3-adrenergic agonist, increased heart rate, but changes in blood pressure and cardiac output were not significant. The drug decreased blood flow in the brain, the spleen and the kidneys, but markedly increased it in BAT. At 2 mg/kg, arotinolol, an alpha/beta-adrenergic blocker, decreased blood pressure by 20 mmHg and increased cardiac output by 95 ml/min/kg. It slightly but significantly decreased blood flow in the liver and the spleen, but markedly increased the flow in BAT. Acebutolol, a beta 1-adrenergic blocker, decreased blood flow in the liver, the spleen, the pancreas, the kidneys, the adrenals, the skeletal muscle and the skin. Bunazosin, an alpha 1-adrenergic blocker, decreased it in all organs and tissue expect the brain and BAT. The pattern of redistribution of blood flow by arotinolol was very similar to that caused by BRL-26830A. Acebutolol and bunazosin rather decreased the blood flow in the BAT. These results indicate that stimulation of beta 3-adrenergic receptors, in BAT results in vasodilation, and that arotinolol may bind to those beta 3-adrenergic receptors.