Plasma level of norepinephrine, cyclic AMP and cyclic GMP in essential hypertension.

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Abstract
Mean concentration of plasma norepinephrine of 66 normal subjects was 0.23 .+-. 0.02 ng/ml, but that of 81 hypertensives was 0.25 .+-. 0.02 ng/ml. There was no significant difference of plasma norepinephrine concentration between the normotensives and hypertensives. A significant correlation was demonstrated between the concentration of norepinephrine and age in the normotensives (r = 0.51, P < 0.001). This correlation was not found in the group with essential hypertension. Age matching revealed a significant higher concentration of norepinephrine in the 20''s and 30''s and no significant difference in the 40''s and the 50''s. There were also significant negative correlations between the concentration of norepinephrine and both the percent changes in mean blood pressure (r = -0.32, P < 0.005) after 20 min in the recumbent position in the clinic. Mean concentration of plasma cAMP and cGMP of 70 normal subjects were 17.7 .+-. 0.4 and 4.3 .+-. 0.02 pmol/ml, respectively. There was a significant correlation between the concentration of plasma cGMP and age (r = 0.30, P < 0.001) and no correlation between the concentration of cAMP and age in normal subjects. Mean concentration of plasma cAMP of 68 hypertensives was 25.0 .+-. 0.8 pmol/ml and significantly higher than normal subjects (P < 0.001). That of cGMP of the same patients was 4.4 .+-. 0.2 pmol/ml, and there was no significant difference between the normotensives and the hypertensives. Sympathetic nervous activity apparently was not elevated in older patients with essential hypertension but was elevated in younger patients. The 2nd messenger system of cAMP apparently was augmented in all patients with essential hypertension.