EFFECTS OF OUABAIN AND METABOLIC INHIBITING FACTORS ON Ca DISTRIBUTION DURING K-INDUCED CONTRACTURE IN GUINEA PIG TAENIA COLI

Abstract

It was reported that an application of high-K (isotonic, 40 mM) caused an increase in oxygen consumption accompanied by an increase in tension change in guinea pig taenia coli (1) and that these changes were reversibly abolished by a depletion of Ca from the high-K medium and Sr could replace Ca only for oxygen consumption (2). These results suggest that Ca entering smooth muscle treated with high-K probably increases oxygen consumption, independent of an increase in muscle tension. In a previous paper (3), effects of factors inhibiting tension development on oxygen consumption of the muscle in high-K medium were reported. Glucose removal from the high-K medium abolished the already developed tension corresponded with a decrease in the elevated oxygen consumption rate. Addition of DNP (1×10-4M) to high-K medium further increased or maintained the increased oxygen consumption although it abolished the already developed tension, and the change in oxygen consumption was not modified by Ca removal. On the other hand ouabain (2.5×10-6 M) maintained the increased oxygen consumption in high-K medium, but almost abolished the developed tension. The increase in oxygen consumption was dependent on external calcium. In the present paper, effects of factors inhibiting high-K induced tension and/or oxygen consumption on Ca distribution in taenia coli are studied and this throws some light on a participation of Ca distribution in changes in tension and oxygen consumption of the muscle in high-K medium. A study on ouabain and DNP with high-K on Ca exchange in taenia coli has been reported by Pfaffman and Holland (4), which is incompatible with the present data.