Effect of exercise on isoprenaline-induced lymphocyte cAMP production in atopic asthmatics and atopic and non-atopic, non-asthmatic subjects

Abstract

The effect of exercise on isoprenaline‐induced cyclic adenosine monophosphate (cAMP) production was studied in peripheral‐blood lymphocytes obtained from ten patients with atopic asthma, seven subjects who were atopic but did not have asthma and eight non‐atopic, non‐asthmatic control subjects. The asthma in the atopic subjects was mild only requiring intermittent treatment with inhaled β adrenoceptor agonists, none of which were taken in the 48 hr prior to the study. Exercise consisted of a standardized 6‐min run on a treadmill sufficient to raise the subject's pulse rate to > 160 bpm and respiratory function was measured before and at 5,10,15,20,30 and 60 min after the test. Blood samples were taken 5 min before and at 10 and 60 min after exercise, lymphocytes were separated by density gradient centrifugation and cAMP measured by a competitive radioimmunoassay. Exercise led to a significant decrease (27%) in the forced expiratory volume in I sec (FEV₁) in the ten atopic asthmatic subjects but no change (< 3%) in the non‐atopic and atopic non‐asthmatics. There was no significant difference in the unstimulated cAMP levels before exercise in the three groups, but stimulation with isoprenaline caused a significantly greater rise in cAMP in the non‐atopic, non‐asthmatic subjects when compared to both the atopic asthmatics and the atopic subjects without asthma. Exercise led to a significant elevation of cAMP in all three groups of subjects, but the same differences between the groups remained. These results suggest that there are differences in lymphocyte β receptor function not between patients who are asthmatic or non‐asthmatic but between individuals who are atopic as opposed to non‐atopic.