Cryoactivation fails to augment plasma renin activity in the cat.

1. Active and cryoactivated renin (plasma renin) activity after incubation at -5 degrees C for 4 days, were measured in cat plasma sampled before and during the following procedures: suprarenal aortic stenosis, electrical stimulation of the pons and mild hypotensive haemorrhage. 2. Under all experimental conditions the values of plasma renin activity for both the activated and non-activated samples were similar. 3. The absence of a cryoactivatable aliquot of renin suggests that in cat plasma the inactive form of the enzyme either is actually absent or has a liability to the action of cold different than in other animal species.