RELATION OF THE GROUPS OF THE ADRENALIN MOLECULE TO ITS CARDIO-ACCELERATOR ACTION

Abstract

Equivalent cardio-accelerator inj. rates for adrenalin and simpler phenylethylamine derivatives (arterenol, epinine, neosynephrin, and synephrin) were detd. by electrocardiographic records from normal and from adrenaldemedullated, unanesthetized dogs. The responses of the denervated hearts of dogs with adrenals intact were indistinguishable from the responses of the adrenal-de-medullated dogs. Rapid development of refractoriness to adrenalin did not develop in the sino-auricular node as it did in the intestinal smooth muscle. Each of the compounds accelerated the denervated heart when given in concs. having any effect on the heart rate, and the degree of acceleration increased with increase in dosage. Removal of the -CH3 of the amino group of the adrenalin molecule did not significantly alter the cardio-accelerator potency, but removal of any one of the three -OH groups resulted in a compound 1/25 to 1/2500 as potent as adrenalin. The greatest loss of accelerator potency occurred on removal of the meta -OH group. Removal of the para -OH group reduced the cardio-accelerator potency more than it reduced the pressor potency.