Bronchomotor tone in protein-energy malnutrition

The study examined the reactivity of the tracheobronchial tree of rats maintained on low protein and tryptophan-deficient diets. It was found that: (1) Rats maintained on 5% protein or tryptophan-deficient diets showed little or no weight gain. A 15% protein diet was adequate for normal growth of female rats, but not of male rats. (2) Airways of malnourished rats showed significant bronchoconstriction when treated to an acetylcholine (AcCh) concentration of 10(-11) M. The threshold concentration of AcCh for normal rats was 10(-5) M. Airways of malnourished rats were also more sensitive to cold. (3) Rehabilitation of the malnourished rats attenuated the response to AcCh. Recovery, however, was not complete. (4) Prior application of phentolamine and atropine markedly reduced the sensitivity of the airways of malnourished rats to AcCh. The results seem to indicate that alpha-adrenoceptors and the vagus nerve may be involved in the observed increased reactivity of airways of malnourished rats.