Angiotensin and renin in rat and dog brain

An enzyme with the characteristics of classical renin was isolated from brain extracts of nephrectomized dogs. This enzyme is thermolabile, nondialyzable, and forms a vasoconstrictive material when incubated with renin plasma substrate at pH 7. A short lasting pressor activity was also found in brain extracts of dogs and rats. This activity was due to a substance identified by chemical and pharmacological tests as angiotensin. Countercurrent distribution of brain extracts of rats showed that 38% of the pressor activity corresponded to angiotensin II and the remainder to angiotensin I. A remarkable correlation was found between angiotensin and norepinphrine concentrations in different portions of the encephalon of the dog.