The term intrinsic sensitivity and its application to the vasopressor action of noradrenaline and vasopressin in arteriosclerotic rats.

The intrinsic sensitivity, i.s., as the quotient of the maximum of the cumulative dose-response curve of an agonist in a pathologically or otherwise changed target object to the maximum of the cumulative dose-response curve of the agonists in the normal target object, has been used to characterize the reaction ability for vasoconstriction of the blood vessel system of the isolated perfused hind legs of arteriosclerotic rats (pretreatment with vitamin D2) on the injection of noradrenaline (NA), 8-lysine-vasopressin (LVP), and a vasopressin preparation with an admixture of oxytocin (VA), respectively. I.s. was found to be 0.80 to NA, 0.32 to LVP, but 1.27 to VA. That means that reaction ability for vasoconstriction of the blood vessel system of vitamin D2-pretreated arteriosclerotic rats is decreased for certain agonists but is increased for others. pD2 value of NA was found to be 4.69 in normal rats and 4.85 in vitamin D2-pretreated rats. The respective data were 5.80 and 6.32 for LVP and 3.58 and 3.88 for VA. Comparing EAm in normal rats, the relation of NA, LVP, VA, prostaglandin F2 alpha, and angiotensin II was about 1 : 1 : 06 : 0.25 : 0.15.