Decreasing effects of glycerol-fractions extracted from ox diaphragm muscles on acetylcholine-induced contractions of smooth muscles.

Extracts of 5% glycerol obtained from ox diaphragm muscles were fractionated into four (A, B, C and D) with (NH4)2SO4. The activity as acetylcholine (ACh) receptor-like substance containing fraction was evidenced as follows; the ACh-induced contraction of tracheal muscles decreased with addition of the fraction, and such could not be attributed to the reaction with ACh receptors of tracheal smooth muscles. Fraction D had the most potent activity in the presence of neostigmine. This reaction induced by fraction D was reversed by addition of d-tubocurarine (d-TC). Fraction D was fractionated into three (I, II and III) by gel filtration on Sephadex G-75 with 50 mM phosphate buffer (pH 7.5). The purified fraction III was identified by electrophoresis, UV and visible absorption spectrum, and ion-exchange chromatography to be myoglobin. Pure myoglobin also proved to have a decreasing effect on ACh-induced contraction.