Physical activity decreases the number of beta-adrenergic receptors on human lymphocytes

On intact human lymphocytes a specific binding site (BS) for 125I-Cyanopindolol (125I-CYP), a derivative of the beta-blocking drug pindolol, was characterized. Inhibition of binding for catecholamines in the following order of potency: l-isoprenaline greater than l-adrenaline greater than l-noradrenaline proves the BS as a beta 2-receptor subtype. In 77 healthy persons (36 females, 41 males) the number of BS amounted to 2,639 +/- 125 BS/cell without any significant correlation to age (17-86 years) or sex. The dissociation constant (KD) indicating the affinity of iodocyanopindolol to the BS on intact lymphocytes was KD = 1.9 +/- 1.1 X 10(-10) M. A change of the number of beta-adrenergic receptors on intact human lymphocytes has been measured previously in asthmatics and in the myocardium of patients with congestive heart failure. We investigated a possible change in the beta-receptors on lymphocytes by physical and mental activity ("stress") in physicians going about their daily routine work. Persons left alone in a hospital room reading or sleeping were defined as "inactive controls". The number of BS on intact lymphocytes was significantly higher in inactive persons at 8 a.m. (2,230 +/- 482 BS) compared to active persons (1,743 +/- 285 BS; P less than 0.05) and at 1 p.m. (2,394 +/- 253 BS vs 1,733 +/- 556; P less than 0.05) but not different at 6 p.m. (1,634 +/- 578 BS vs 1,768 +/- 588 BS; P less than 0.1). The KD remained unchanged under all conditions. The serum noradrenaline and adrenaline levels were also measured during the day.(ABSTRACT TRUNCATED AT 250 WORDS)