Smooth muscle contractility and changes in histaminergic mechanisms in the pig trachea during development

Maximal contractile reactivity was compared in isolated tracheas from different sized (aged) pigs. Maximum force and tension to histamine declined by approximately 10-fold in tracheas from 150-200 kg pigs compared to 30 kg animals, whereas acetylcholine-induced contractions were little changed. Furthermore, contractions to Ca2+ in chemically skinned muscle were not different in different sized animals. The effect of maturation on the reactivity to histamine was unaltered in preparations from which superficial connective tissue had been dissected but it was reduced or abolished by preincubation with indomethacin. The data indicate that maturation affects histaminergic mechanisms of contraction selectively, with respect to acetylcholine, rather than the intrinsic contractile properties of the muscle.