The influence of carotid body stimulation on oxygen tension and microcirculation of various organs of the cat.

To determine the importance of chemoreflex control for microcirculation, we investigated tissue pO2 and local flow on the surface of muscle, kidney, liver, and heart under systemic hypoxia and under isolated hypoxic perfusion of the carotid body in anaesthetized (pentobarbital) and artificially ventilated cats. Under systemic hypoxia, local blood flow mainly decreased in muscle and kidney, whereas liver and heart showed a flow distribution mainly with a flow decrease. Under systemic hypoxia, tissue pO2 decreased to values in the range of 0 to 10 Torr. A linear relationship was found between the pO2 change under hypoxia and the normoxic pO2 in the investigated organs, indicating local regulatory mechanisms of microcirculation. Isolated hypoxic perfusion of the carotid body caused a microflow increase in kidney in about 63%, in liver in about 55%, and in heart in all cases. Hypoxic perfusion of the carotid body caused pO2 increases in kidney and liver with mean pO2 values of 3 and 4 Torr, respectively, whereas, it produced no significant pO2 change in heart and muscle. The pO2 changes in kidney and liver significantly depended on the normoxic basic tissue pO2 level, indicating, in connection with local flow increases, a redistribution of local flow in these organs.