EFFECT OF PHENYLETHANOLAMINE N-METHYLTRANSFERASE CONCENTRATION AND SPECIES-DIFFERENCE ON INHIBITORY POTENCY OF SKANDF 64139

  • 1 January 1977
    • journal article
    • research article
    • Vol. 17  (2) , 201-213
Abstract
The potency of SK&F 64139 [7,8-dichloro-1,2,3,4-tetrahydroisoquinoline hydrochloride] in inhibiting rabbit adrenal phenylethanolamine N-methyltransferase (PNMT) appears to be a function of protein concentration when high concentrations of the latter are employed. At lower enzyme levels the degree of inhibition produced by the drug becomes independent of PNMT, allowing for the proper calculation of an inhibition constant. The Ki for the compound under these circumstances was 3 nM. Inhibitor Kd within the same order of magnitude were subsequently obtained using the adrenal enzyme obtained from the rat, cow, dog, human and squirrel monkey. The PNMT receptor sites for SK&F 64139 probably do not differ substantially from species to species. The general utility of this drug as an inhibitor of adrenal epinephrine biosynthesis is suggested.

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