Effect of systemic adenosine infusion on capillary flow and oxygen pressure distributions in skeletal muscle of the rabbit.

The aim of this study was to investigate the effect of systemic adenosine (ADO) infusion on blood flow and oxygenation at the capillary level in skeletal muscle in order to estimate oxygen demand. In anesthetized rabbits, a multiwire microelectrode was placed on the left vastus medialis muscle surface, and was used for capillary flow (determined by hydrogen clearance) as well as for oxygen pressure (PtO2) measurements. Laser Doppler flowmetry (LDF) was also used on the contralateral muscle surface for regional microcirculatory blood flow measurements. ADO infusion (50-100 micrograms/kg/min) was given in a central vein. During the ADO infusion the mean arterial blood pressure decreased from 81 +/- 5 (mean +/- SD) to 64 +/- 4 mmHg (a 21% decrease) (p < 0.001), while capillary flow decreased by 37% from a mean value (relative units) of 1.0 +/- 0.84 during control to 0.63 +/- 0.72 (p < 0.001). During ADO infusion there was an increased flow heterogeneity. The mean PtO2 increased by 29% from 5.6 +/- 2.3 to 7.2 +/- 2.2 kPa (p < 0.001) associated with decreased oxygen heterogeneity. A 43% reduction of the relative calculated local oxygen consumption was found during ADO infusion (p < 0.05). The LDF flux decreased by 7% (p < 0.05). We conclude from these results that systemic adenosine infusion decreases skeletal muscle capillary blood flow and in parallel increases the oxygen pressures. This can be explained by a redistribution of the capillary blood flow as well as a reduction in skeletal muscle oxygen demand.