Biochemical evaluation of sympathetic nerve tone in essential hypertension

The concentration of plasma catecholamines (CA), serum dopamine beta-hydoxylase (DBH) activity and plasma renin activity (PRA) were simultaneously measured in 55 patients with essential hypertension (EH). Further the enzyme activities of CA biosynthesis in human vas deferens excised at elective vasectomy were related with the blood pressure, plasma CA, serum DBH of 57 men at the time of vasectomy. Total plasma CA and norepinephrine (NE) were increased in 28 and 35% of patients with benign EH, respectively. Total plasma CA were also increased in 45% of men with elevated blood pressure prior to vasectomy. Total plasma CA were correlated with diastolic blood pressure in EH (p less than 0.01). Further, in men with normal and raised blood pressure prior to vasectomy, there was a significant correlation of total plasma CA with systolic and diastolic blood pressure (p less than 0.01). Total plasma CA were correlated with PRA in patients with EH (r=0.497, p less than 0.001). Capacity for NE biosynthesis, vas deferens tyrosine hydroxylase (TYH) activity and dopa decarboxylase (DDC) activity were increased in men with raised blood pressure. There was a direct correlation of total plasma CA with the activities of TYH and DDC (r=0.46, and 0.54, p less than 0.005). Increased sympathetic nerve tonicity associated with increased neurotransmitter biosynthesis may be an important factor responsible for blood pressure elevation in men prior to vasectomy and in others with EH. The some patients with EH may have a renin-catecholamine relationship and both pressor systems may be linked to be a pathogenic factor for the elevation of blood pressure.