Effects of homopantothenic acid on intestinal smooth muscles.

Abstract

The effects of homopantothenic acid (HOPA) on intestinal smooth muscles were investigated and compared with those of y-aminobutyric acid (GABA). HOPA contracted the rat ileum and produced a biphasic response (relaxation followed by contraction) in the guinea-pig ileum and taenia coli. Half-maximal effects were obtained with 0.3-0.9 nM HOPA and maximal responses with 2-4 nM in the rat and the guinea-pig ileum. In the guinea-pig taenia, half-maximal effects were obtained with 0.2-0.25 ,uM HOPA and maximal responses with 2-4 ,uM HOPA. Tachyphylaxis occurred with higher concentrations. All these responses were not significantly affected by tetrodotoxin (TTX), atropine, diphenhydramine or metiamide. The relaxation elicited by HOPA was not reduced by simultaneous application of phentolamine and propranolol. Unlike HOPA, GABA produced a biphasic response (a relaxation followed by a contraction) in the guinea-pig ileum, which was almost abolished by TTX. These results suggest that HOPA mainly acts on intestinal smooth muscle directly, whereas GABA does indirectly through nerves.homopantothenic acid (HOPA) ; y-aminobutyric acid (GABA); rat ileum; guinea-pig ileum; guinea-pig taenia coli

Effects of methylmercuric chloride and bis (methylmercuric) selenide on responses of isolated intestinal smooth muscle of the guinea-pig.

“…The strip trimmed approximately 1 cm in length was suspended in a small organ bath and perfused with the modified Krebs solution (Fukushi and Suzuki 1983). The bath was gassed with 95% OZ and 5% COZ and its temperature was kept at 34° C. The resting tension of each strip was adjusted at 200 mg and the changes in tension induced were recorded isometrically with a force transducer (Grass, FT-10).…”