renin /rē″nin/ [L, ren, kidney] , a renal proteolytic enzyme, produced by and stored in the juxtaglomerular apparatus that surrounds each arteriole as it enters a glomerulus. The enzyme affects the blood pressure by catalyzing the change of angiotensinogen to angiotensin I, which is then converted to angiotensin II, strong pressor. Normal findings of adult plasma renin, measured in an upright position and sodium depleted, are 2.9 to 10.8 ng/mL/hr. Should not be confused with rennin.
