[Beta-adrenergic receptors and plasma catecholamine behavior in trained and untrained athletes]

6 sports students (VO2 max. 54.0 +/- 2.6 ml/kg . min) and 6 marathoners (VO2 max. 65.7 +/- 2.0 ml/kg . min) performed graded treadmill tests. Free plasma catecholamines (noradrenaline and adrenaline), heart rate, lactate were assessed at rest and during exercise. The behaviour of beta-adrenergic receptors of polymorphonuclear leukocytes was estimated additionally before the treadmill test. The maximum running velocity was 14.6 +/- 0.8 km/h (sports students) and 17.3 +/- 0.6 km/h (marathoners). Noradrenaline was approximately 46% (v = 12 km/h) to 67% (v = 14 km/h) lower in the group of marathoners than in sports students; adrenaline showed no or smaller differences between both groups. No significant differences in the plasma catecholamine behaviour occurred between the groups at rest and during maximum exercise. Specific binding of 3H-Dihydroalprenolol to intact cells was higher in the marathoners than in sports students (p greater than 0.01). Scatchard analysis revealed a maximum binding of 21.1 fmol/10(7) cells (sports students) and 35.3 fmol/10(7) cells (marathoners), which indicated approximately 1,300 (sports students) and 2,150 binding sites cell (marathoners). Inverse correlations between noradrenaline (r = -0.63), VO2max. (r = -0.79) and the specific binding of 3H-DHA were observed. The reduction of plasma catecholamines (approximately 46-67%) and the increase in specific binding sites (approximately 67%) were in the same range.(ABSTRACT TRUNCATED AT 250 WORDS)