THE DYNAMIC-RESPONSE OF THE BETA(2)-ADRENOCEPTOR AND ALPHA(2)-ADRENOCEPTOR IN HUMAN BLOOD-CELLS TO PROLONGED EXHAUSTING STRAIN, SLEEP AND ENERGY DEFICIENCY

Leucocyte beta2-receptors and platelet alpha2-receptors were studied d uring a five days ranger training course with heavy physical activitie s day and night, energy deficiency and almost without sleep. The beta2 -adrenoceptors on granulocytes and mononuclear cells decreased to a mi nimum density and affinity after 2 and 4 days of activities respective ly. For the rest of the course the beta2-receptors increased, however, without reaching control values at the end of the course. A significa nt decrease of about 15 % was found on day 3 in both platelet alpha2-r eceptor density and affinity followed by an up-regulation to about 20% above control levels on day 5. A significant correlation (r=-0.6 to-0 .8) between the beta2-receptor density and affinity, and the plasma ca techolamines was recorded during the first 2-3 days, indicating a homo logous down-regulation. The regeneration of receptors in spite of high catecholamines reflects a predominance of heterologous up-regulation during the second half of the course The results indicate that beta-ad renergic receptor down-regulation contributes to attenuation of the ad renergic responsiveness during the first 2-3 days of exhausting physic al activities, but is not sufficient to account for the desensitizatio n seen after longer periods of stress.