Effects of Isometric Exercise on Blood Cell Adrenoceptors in Essential Hypertension

Abstract

The effect of handgrip (HG) isometric exercise on plasma catecholamines, α₂-adrenoceptors on platelets and β₂-adrenoceptors on lymphocytes was studied in normotensive subjects (NT) and essential hypertensive subjects (HT). Whereas systolic blood pressure (SBP) increases were similar in NT and HT subjects, diastolic blood pressure (DBP) and heart rate (HR) increased more in the former group. Baseline values and changes in plasma epinephrine (E) and norepinephrine (NE) did not differ between both groups. No differences were apparent in α₂-adrenoceptor density and affinity between NT and HT subjects before or after the test. HG isometric exercise induced a similar increase in β₂-adrenoceptors on lymphocytes of 22 ± 7 and 13 ± 5% in NT and HT subjects, respectively. Affinity to the β₂-adrenoceptors under baseline conditions was somewhat lower in HT (8.1 ± 0.4 pM) than in NT subjects (6.5 ± 0.5 pM), and this difference persisted during the test. Our results indicate that there are no differences in α₂- and β₂-adrenoceptor densities either at baseline conditions or after HG isometric exercise between NT and HT subjects. Small differences noted in affinity to the β₂-adrenoceptors require further investigation.