Beta adrenoceptor control of the microvascular reserve in XXXX myocardium.

@entity3045 @entity2822 @entity95 @entity6310 @entity2165
This study was performed to determine if the unperfused microvascular reserve in the @entity95 heart can be controlled by beta adrenoceptors. Anesthetized, open chest @entity95 (N = 54) were subjected to saline i.v., 0.7 mg/kg of @entity2165 i.v., 1 mg/kg of @entity6310 , 0.1 microgram/kg of @entity3045 , 1 microgram/kg of @entity3045 or 0.7 mg/kg of @entity2165 + 1 microgram/kg of @entity3045 treatments. In half these animals coronary flows were determined before and after treatment using radioactive microspheres. The others were given 100 mg/kg of @entity2822 -dextran and the hearts were removed and analyzed for perfused and total microvascular morphology. The fluorescence marked the perfused microvessels and the slides were stained to show all vessels. Control group blood flow was 213 +/- 25 ml/min/100 g. Flows decreased 25% with @entity2165 and @entity6310 whereas no change was seen with @entity3045 or @entity2165 + @entity3045 . Total capillary volume fraction ranged from 0.15 to 0.20 mm3/mm3 with 60% of this perfused in controls. @entity2165 significantly reduced this to 47% whereas @entity6310 (90%), high-dose @entity3045 (97%) and @entity3045 + @entity2165 (99%) resulted in a significant mobilization. Low-dose @entity3045 resulted in a mobilization of capillaries to a degree intermediate (79%) between controls and high-dose @entity3045 . Total arteriolar volume fraction ranged from 0.002 to 0.004 mm3/mm3 and in controls 65% of this was perfused. This percentage was reduced with @entity2165 and significantly increased with all other treatments except @entity6310 . Thus, blockade of beta-1 adrenoceptors results in decreases in the percentage of perfused microvessels whereas stimulation of beta-2 adrenoceptors results in an increase.(ABSTRACT TRUNCATED AT 250 WORDS)
