PATIENTS WITH MILD ESSENTIAL HYPERTENSION HAVE INCREASED PLATELET SIZE AND RELEASE REACTION ANO SHOW INCREASED RECEPTOR RESPONSE TO INFUSED ADRENALINE

 

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Hypertensive (n = 35) and normotensive {n = 44) men all 42 years old were studied. The hypertensive (HT) had larger venous platelets than the normotensive (HT) (7.46 ± 0.10 vs 7.12 ± 0.09 10^-15 1, p = 0.01). Plasma concentration of |3-thromboglobulin (BTG) was increased in arterial blood in hypertensive (40 ± 8 vs 21 ± 2 ug/1, p=0.02) while the venous values were similar in the two groups. Despite similar sampling procedure, the normotensive subjects had markedly higher BTGconcentration in venous compared to arterial blood (p≺0.01) at variance from thehypertensive where the arteriovenous difference in plasma BTG concentration was not present. Adrenaline was infused to 13 hypertensive and 12 normotensive subjects with dose gradually increasing to 0.04 pg/kg/min. Forearm blood flow was measured by strain gauge technique and relative forearm resistance calculated as mean blood pressure divided by flow. Twelve normotensive subjects (control group) received saline infusion.

Change in forearm resistance reflectsβ₂- activation of smooth vascular cells, change in platelet count reflects splenic liberation of platelets in response to adrenergic stimulation while change in BTG may reflect platelet release upon stimulation of α₂ -receptors. Thus, middle aged men with essential hypertension show increased sensitivity to adrenaline infusion in vascular smooth muscle, spleen and platelets.