Interscapular Brown Adipose Tissue Blood Research Articles

Intravenously infused adenosine increases the blood flow to brown adipose tissue in rats

The effects of intravenously infused adenosine (ADO) and its analogues, N 6-R(−)-phenylisopropyladenosine (R-PIA), 5′-N-ethylcarboxamide adenosine (NECA), on the blood flow to interscapular brown adipose tissue were studied in urethane-anesthetized rats. ADO and NECA, but not R-PIA, caused a dose-dependent increase in interscapular brown adipose tissue blood flow. The relative potency of these compounds to increase this blood flow was NECA > ADO > R-PIA. Infusing R-PIA and NECA intravenously caused a fall in diastolic blood pressure and heart rate whereas an infusion of ADO up to 380 nmol/rat per min did not elicit any systemic cardiovascular effect. A 10-mg/kg dose of alkylxanthines such as caffience, 8-phenyltheophylline (8-PT) and 8-sulfophenyltheophylline (8-SPT) inhibited the half-maximum responses of interscapular brown adipose tissue blood flow to ADO by 41, 71 and 65% respectively indicating that caffeine is less potent than 8-PT and 8-SPT. The ADO uptake inhibitor, dipyridamole, significantly potentiated the ADO effect. These results suggest that the increased interscapular brown adipose tissue blood flow caused by ADO might possibly be mediated by A 2 receptors.