RENAL VASCULARITY IN THE DOG—ALPHA-ADRENERGIC BLOCKADE AND ACUTE HEMORRHAGE

1. Alpha-adrenergic block effects changes in the appearance of the angiogram as compared to that of the control study in the anesthetized dog, manifested by an increase in size of the renal vessels. There is apparently a degree of constriction of the renal vessels in the anesthetized dog.

2. In hypovolemic hypotension after alpha-adrenergic block the angiogram shows only slight, if any, changes in the renal vessels. This differs markedly from the changes in hypovolemic hypotension without Dibenzyline pre-treatment where all renal vessels showed diminution in size.

3. After hemorrhage in the untreated dog there is evidence of redistribution of intrarenal blood flow with diversion of blood away from the cortex as shown by irregularity of the cortical nephrogram. In hypovolemic hypotension after Dibenzyline the diversion of blood away from the cortex is much less marked or not apparent.

4. Intravenous epinephrine in the hemorrhaged, Dibenzyline pre-treated dogs effected no change or increase in caliber of the renal arteries. This differs from the marked vasoconstriction resulting from epinephrine administered to the hemorrhaged dog without alpha-adrenergic block.

5. In hypovolemic hypotension the vasoconstriction is most marked in the cortex with diversion of blood away from the cortex very likely related to endogenous catecholamine action mediated by increased activity of the sympathetic nervous system. This effect is precluded or diminished by alpha-adrenergic blockade.

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