The content of free-catecholamines in blood platelets is much higher than in plasma
and platelet catecholamines must be taken up from plasma, since platelets lack the
enzymes for catecholamine synthesis. There is some evidence that platelet catecholamine
content under certain circumstances may be an integrated measure of plasma catecholamine
concentrations over time. Platelet-free catecholamines were therefore assayed in 18
untreated patients with essential hypertension and in 16 normotensive control subjects.
Mean platelet-free dopamine in the hypertensive group was 3.7 ± 0.4 pg/mg platelet
weight, i.e. significantly less than the 6.5 ± 0.9 pg/mg found in the normotensive
(p <0.005). Platelet contents of noradrenaline and adrenaline did not differ. Decreased
platelet-free dopamine and unchanged platelet noradrenaline and adrenaline persisted
after adjustment for increased body weight in the hypertensive group. Although the
reasons for decreased platelet-free dopamine in the hypertensive group remain unknown,
this finding may add to previous result showing facilitated release of granular contents
from blood platelets in patients with essential hypertension. Our data do not support
platelet levels of free-catecholamines to be a marker of increased sympathetic tone
in essential hypertension.
Keywords
Adrenaline - Dopamine - Essential hypertension - Noradrenaline - Platelet catecholamines
