Hypertension from Carotid Occlusion Decreases Renal Papillary Plasma Flow, Hypotension from Hemorrhage Increases It, an Autoregulatory Paradox

Renal papillary plasma flow was tested during acute increases and decreases of perfusion pressure using the 125I-labelled albumin technique. Increases of pressure were attained through ligation of carotid arteries; decreases of pressure through modest hemorrhage. In 12 control rats with blood pressure of 144mmHg, the papillary plasma flow averaged 21.5ml per 100g papilla per min. In 12 rats after ligation of carotid arteries, blood pressure rose from 143mmHg to 172, a 20% increase. The papillary plasma flow in these rats with acute hypertension averaged 17.9ml per 100g papilla per min, a 17% decrease (p