A comparison of cardiovascular and catecholamine responses to three stimuli in mild hypertension

In five males with mild essential hypertension, simultaneous hemodynamic and arterial and venous plasma catecholamine responses to three stimulation tests (mental arithmetic, isometric handgrip exercise, and cold) were studied. Plasma norepinephrine (NE), epinephrine (EPI), and dopamine (DA) were measured radioenzymatically. Isometric exercise was the best stimulus for systolic and diastolic blood pressure and NE. Mental arithmetic produced the highest levels of plasma EPI, but there was great intersubject variability. Dopamine levels did not increase with any of these stimuli. Consistent arterio-venous differences across the forearm were seen for EPI but not NE, consistent with local production of NE. Isometric exercise produced the closest correlations between peripheral plasma catecholamine levels, blood pressure, and heart rate. Good correlations were seen with mental arithmetic, but with the stimulus of cold correlation was poor.