The effect of noradrenaline infusions and adrenergic blocking agents on serum glutamic–oxalacetic transaminase in dogs

Abstract

Mongrel dogs were infused with 6, 96, or 384 μg/kg of noradrenaline at a constant rate for 1 h. Serum glutamic–oxalacetic transaminase (SGOT), blood pressure, and heart rate were recorded during and for 10 h after the infusion. There was no change in SGOT levels at the lowest dose of noradrenaline. The SGOT activity was increased at the end of the infusion of the 96 μg/kg dose. The 384 μg/kg dose caused the SGOT activity to more than double by the end of the infusion and to more than triple 10 h later. Blood pressure increased with only the two larger doses of noradrenaline. Animals infused with 384 μg/kg of noradrenaline and pretreated with either phenoxybenzamine or propranolol showed a delayed rise in SGOT activity. Neither of these drugs alone blocked increases in SGOT activity but a group pretreated with both blocking agents showed no increase in enzyme levels. The hypertension due to the vasoconstriction produced by noradrenaline may be accompanied by hypoxic conditions in the tissues, and this hypoxia may cause changes in membrane permeability of sufficient magnitude to allow release of the GOT enzyme. The adrenergic blocking agents may reduce or eliminate the pressor response to noradrenaline and thus reduce the hypoxia.