Inhibition of the cardiac inotropic effect of phenylephrine by a tetramine disulfide with irreversible α-adrenoceptor blocking activity

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Abstract
The newly synthesized α-adrenoceptor blocking drug BHC (N,N′-bis[6-(o-methoxybenzyl-amino)-n-hexyl]cystamine) was found to block irreversibly the positive inotropic effect of the sympathomimetic drug phenylephrine on the isolated rat left atrium.BHC was used to test the adrenoceptor interconversion hypothesis which claims that low temperature converts inotropic β-adrenoceptors in rat atrium and frog ventricle to α-adrenoceptors.There was no evidence of adrenoceptor 'interconversion.' In the rat atrium low temperature did not increase the BHC antagonism of phenylephrine and did not cause BHC to inhibit the inotropic effect of noradrenaline or isoprenaline. In the perfused frog heart low temperature did not lead BHC to inhibit the inotropic effect of phenylephrine, adrenaline, or isoprenaline.