Because of high plasma concentrations of conjugated
catecholamines and their unknown relationship to
hypertension, we determined those conjugates more specifically as
catecholamine sulfates together with the sulfoconjugating
enzyme-phenolsulfotransferase activity in platelets of 62 patients with
essential hypertension and 32 normal controls. Our results indicated: (1) that the pool of total (free and sulfated)
catecholamines (
dopamine,
norepinephrine, and
epinephrine) is higher (because of an increase in
dopamine sulfate levels) but the degree of
epinephrine conjugation is lower in patients with
essential hypertension compared with controls; (2) that
norepinephrine sulfate levels rise with age in both groups, but the increase in free
norepinephrine with age observed in controls was not observed in patients with
essential hypertension; and (3) that
catecholamine conjugates were found to be exclusively
sulfates and platelet phenolsulfotransferase activity was not different in both groups. Platelet phenolsulfotransferase activity was, however, positively correlated with plasma
norepinephrine sulfate levels, and the degree of sulfoconjugation of
norepinephrine was positively correlated with that of
dopamine in controls but not in patients with
essential hypertension. These abnormalities occurring in
essential hypertension in the absence of intergroup differences in platelet phenolsulfotransferase activity suggest that the
enzyme is either not a good marker of the overall activity or that other factors account for the observed differences. Thus, additional determinants of the process of generation and degradation of sulfoconjugated
catecholamines, some of which may be more stable markers of sympathetic activity than free
catecholamines, need to be explored.