The effects of cadmium ions on blood pressure, dopamine-β-hydroxylase activity and on the responsiveness of in vivo preparations to sympathetic nerve stimulation, noradrenaline and tyramine

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Abstract
Changes in sympathetic nervous function of the rat caused by acute and chronic treatment with cadmium (Cd2+) have been studied in vivo by measurement of changes in blood pressure and plasma dopamine-β-hydroxylase (DBH) activity. In anaesthetized animals, acute injection of Cd2+ (0·1–1 μm) caused an initial fall followed by a rise in both diastolic and systolic blood pressure, plasma DBH activity increased in a dose-dependent manner. Animals subjected to repeated treatment with Cd2+ (0·5, 1 μm) daily for 12 days became markedly hypertensive, the increases in the systolic pressure being greater than those seen in the diastolic pressure. In pithed animals the blood pressure responses of the treated animals to electrical stimulation of the lower sympathetic outflow (T10-L1) and tyramine injection (35, 70, 140 nmol kg−1) were markedly decreased, whilst responses to low doses of noradrenaline (NA) (7, 15, 30 nmol kg−1) were potentiated compared with untreated animals. In addition, plasma DBH activities following sympathetic outflow stimulation and tyramine administration were markedly increased and decreased respectively compared with untreated controls. The data suggest that a correlation exists between changes in sympathetic nervous function and the induction of hypertension caused by Cd2+.