Celuch SM, Juorio AV. Effects of deuterium substitution on the chronotropic responses to some sympathomimetic amines in the isolated rat atria.
NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1987;
336:391-5. [PMID:
3124004 DOI:
10.1007/bf00164871]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In spontaneously beating rat atria the potencies for the chronotropic effects of the following deuterated phenylethylamine derivatives were higher than the potencies of the corresponding non-substituted (protio-) amines: alpha,alpha,d2-beta-phenylethylamine; alpha,alpha,beta,beta-d4-p-tyramine; alpha,alpha,beta,beta-d4-m-tyramine; alpha,alpha,beta-d3-p-octopamine. In contrast, alpha,alpha,beta-d3-noradrenaline and alpha,alpha,beta-d3-m-octopamine were equipotent with the corresponding protio-amines. Experiments performed in atria depleted of endogenous noradrenaline by pretreatment with reserpine and in atria exposed to the monoamine oxidase (MAO) inhibitor pargyline indicated: a. p-octopamine had both direct and indirect effects, but the chronotropic responses to p-octopamine in tissues with normal MAO activity depended mostly on the direct action of the amine; deuterium substitution enhanced the indirect component of action of p-octopamine; b. m-octopamine possessed considerable indirect effects while d3-m-octopamine behaved as an amine of direct action. The substitution of deuterium for hydrogens in the alpha-carbon of the alkyl-side chain of phenylethylamines decreases the rate of deamination by MAO. Therefore, the results obtained with all the amines, except for m-octopamine and alpha, alpha,p-d3-m-octopamine, could be interpreted in terms of the direct, indirect or mixed action of those compounds and/or of the influence that MAO activity has on the chronotropic responses to these amines. The results obtained with protio- and deuterio-m-octopamine suggested that deuterium substitution, either at the alpha- or the beta-carbon, can alter some other mechanisms in addition to the enzymatic deamination.
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