Correlation between increased dopamine-?- hydroxylase activity and catecholamine concentration in plasma: Determination of acute changes in sympathetic activity in man

Abstract

In 11 healthy untrained volunteers the increase in plasma dopamine-beta-hydroxylase (DBH) activity during graded physical exercise has been examined as a true measure of increased activity of the sympathetic nervous system. The correlation between DBH activity, catecholamine concentration (CA) in plasma and heart rate was studied. When work on an electrically braked bicycle ergometer was gradually increased from 12.5 to 100, 200 and 300 watts there was a linear increase in DBH activity and heart rate; the increase in CA concentrations followed an exponential function. The peak values for DBH activity and CA concentration in plasma after the 300 watt work load (as percentages of the resting levels) were 130+/-3% and 820+/-71%, respectively; the adrenaline concentration in plasma increased only to 150+/-19% (p less than 0.05). There were significant correlations between heart rate and work load, DBH and work load and log CA and work load. The data imply direct correlations between heart rate and DBH, heart rate and log CA and DBH and log CA. The exponential increase in noradrenaline concentration in plasma might be due either to a greater net ""overflow'' from sympathetic nerve endings, and/or to increased secretion by the adrenal medulla. In the latter case, the release of noradrenaline would not be accompanied by secretion either of adrenaline or DBH. After work ceased there were sharp falls in heart rate and CA concentration, which indicate an immediate drop in sympathetic activity. DBH activity in plasma returned to normal very slowly; it reached half maximum values after 20-22 min. It is concluded that increased sympathetic activity in man can be estimated in vivo as changes in DBH and/or CA concentration in plasma. In contrast, a rapid decrease in sympathetic activity is directly reflected only by a rapid fall in the plasma concentrations of CA.

Decreased Beta-adrenoreceptor responsiveness as related to age, blood pressure, and plasma catecholamines in patients with essential hypertension.

“…17 Consequently, the relative increase in PNE and PE most likely reflects a (perhaps only slightly) elevated sympathetic tone. 1 Elevated sympathetic activity may be the result of different factors. Thus in young hypertensives, central or perhaps psychodynamic mechanisms may prevail.…”

“…Sympathetic nervous activity and changes therein are reflected in plasma catecholamine concentrations 1 and in heart rate, particularly when parasympathetic tone is minimized during strenuous physical exercise. 8 Beta-adrenoreceptor response can be assessed selectively by heart rate stimulation with isoproterenol.…”

Genetic and familial factors in essential hypertension and related traits

“…Studies consistent with the use of DBH activity as a measure of sympathetic neurotransmitter action are numerous (Wooten and Cardon, 1973;Planz and Palm, 1973;Planz et al, 1975Planz et al, , 1976Ogawa et al, 1976). However, the lack of correlation between DBH activity and catecholamine concentrations under conditions of sympathetic activity led DeQuattro and colleagues (1976) to caution that DBIH is not a reliable index of sympathetic nervous activity in hypertension.…”

“…Its measurement can be accomplished with serum or plasma, and the enzyme assayed in serum or plasma appears to be identical to that found in tissue (Weinshilboum et al, 1973). Studies with chemically sympathectomized rats indicate that the origin of plasma DBH is the sympathetic nerve terminals (Weinshilboum and Axelrod, 1971).Studies consistent with the use of DBH activity as a measure of sympathetic neurotransmitter action are numerous (Wooten and Cardon, 1973;Planz and Palm, 1973;Planz et al, 1975Planz et al, , 1976Ogawa et al, 1976). However, the lack of correlation between DBH activity and catecholamine concentrations under conditions of sympathetic activity led DeQuattro and colleagues (1976) to caution that DBIH is not a reliable index of sympathetic nervous activity in hypertension.…”

Alterations in the responses of the sympathetic nervous system and renin in borderline hypertension.

“…However, in spite of the efforts of many investigators to obtain evidence in support of such a relationship, controversy still abounds. 1 The introduction of improved assay methodology for catecholamines 8 ' 3 has resulted in much new data but a number of problems in interpretation have arisen. Plasma norepinephrine (NE) has been shown to increase with age, 4 with caffeine, 5 with smoking," with sodium restriction, 7 and with activity," and studies which do not control for these variables must be interpreted with caution.…”