Reflex changes in hindlimb and renal vascular resistance in response to distention of the isolated pulmonary arteries of the dog.

We describe a preparation that uses a constant flow, right heart bypass for perfusion of an isolated pouch of the main pulmonary arteries at controlled pressures, and show that increments in pressure in the pulmonary arterial pouch are accompanied by increases in systemic vascular resistance and in hindlimb vascular resistance. These changes are demonstrated over the whole range of 5-120 cm H2O pressure in the pulmonary arterial pouch. In contrast there are no significant changes in renal vascular resistance or heart rate. We find that changing the temperature of the perfusate in the pulmonary arterial pouch from 37 degrees C to 30 degress C is associated with a decrease in systemic vascular resistance. Furthermore, the effects of raising the pulmonary arterial pouch pressure and of cooling are abolished by cervical vagotomy. These findings suggest that there is a tonic reflex vasoconstrictor tone generated by the activity of receptors lying in or close to the walls of the pulmonary artery. These findings also suggest that the differential effects on systemic vascular resistance and renal resistance may provide one mechanism by which changes in blood volume may lead to appropriate changes in renal solute excretion.