1. The response of circulating leucocytes with regard to changes in number, proportion of granulocytes and lymphocytes, as well as changes in the ascorbic acid (AA) concentration of plasma and isolated lymphocytes, were studied in nine men who ran a 21 km race. A marked leucocytosis was noted 5 min after the race, the predominant increase being in granulocytes (P < 0.001) with smaller relative increases in circulating lymphocytes (P < 0.01) and platelets (P < 0.001). Numbers of leucocytes and platelets returned to pre-exercise levels within 24 h after the race.
2. The concentration of AA in plasma increased from 52.7 ± 4.1 μmol/l before the race to 67.0 ± 5.3 μmol/l within 5 min after the race (P < 0.001). This increase in plasma AA concentration was positively correlated with the rise in plasma Cortisol concentration during the race (r = 0.89; P < 0.01). However, within 24 h after the race the plasma concentration of AA fell 20 ± 4% below pre-exercise values (P < 0.01) and remained low for at least the next 2 days (P < 0.05).
3. Lymphocyte AA concentration increased from 15.6 ± 0.6 to 19.7 ± 0.9 μmol/g of lymphocyte protein during the race (P < 0.01) but returned to normal levels within 2 days after the race.
4. It is suggested that the adrenal gland may be the major source of AA efflux into the circulation during exercise.