| Popis: |
The depressant actions of β -mercaptoethylamine (MEA) on the electrically driven isolated guinea pig atrium are compared with those of dichloroisoproterenol, pronethalol, propranolol, dl -erythro-4-(2-methylamino-1-hydroxypropyl) methanesulfonanilide hydrochloride, dl -4-(2-isopropylamino-1-hydroxyethyl) methanesulfonanilide hydrochloride, and isopropylmethoxamine as examples of β -adrenergic blocking agents, and with 2,4-dinitrophenol, iodoacetate, pentobarbital, and quinine as examples of nonspecific depressants. Combinations of these agents with MEA were also examined. The responses studied were catecholamine antagonism, calcium chloride antagonism, and depression of the basal contractile force. MEA was found to have a weak positive inotropic effect on the heart which could not be abolished by the various β -adrenergic blocking agents. MEA also depressed all the responses in a nonspecific manner similar to the effect observed for the metabolic inhibitors. MEA was found to add to the depression caused by all agents tested. A hypothetical model for additive action was tested. The results are consistent with the hypothesis that MEA interferes with some mechanism not related to adrenergic receptor blockade. Metabolic inhibition could not be ruled out as a possible mechanism of action. The myocardial depression seen in the isolated guinea pig atrium may relate to a portion of the cardiovascular effects of MEA and its disulfide, cystamine, seen in the dog and rat. |
