Tissue blood flow changes induced by propranolol infusion in conscious normotensive and renal hypertensive rabbits

Using electromagnetic flowmetry and the radioactive microsphere method, systemic and regional haemodynamic variables in conscious normotensive and hypertensive rabbits were measured. Rabbits were made hypertensive by unilateral nephrectomy combined with cellophane wrapping of the remaining kidney. Systemic and regional haemodynamic effects of propranolol infusions (67 micrograms.kg-1.min-1 for 1 hr, equivalent to a total of 4 mg.kg-1) were compared in the two groups of animals. Propranolol reduced heart rate and cardiac output in both groups of animals studied. The drug only marginally decreased arterial pressure in the normotensive animals but did so more effectively in the hypertensive animals. The difference in the two groups was due to the fact that total peripheral resistance increased significantly in the normotensive but not in the hypertensive rabbits. Regional haemodynamic studies revealed that, in normotensive animals, propranolol decreased blood flow to, and increased vascular resistance in a number of tissues (heart, brain, stomach, mesentery).