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 con sumption rate. Addition of DNP (1 x 10-'m) to high-K medium further increased or maintained the increased oxygen consumption although it abolished the already develop ed tension, and the change in oxygen consumption was not modified by Ca removal. On the other hand ouabain (2.5 x 10-8 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. METHODSStrips of taenia coli isolated from white male guinea pigs were suspended in an organ bath containing Tyrode solution of the following composition (mm); NaC1, 136.8; KCI, 2.7; CaCl2j 2.5; MgCl,, 1.0; NaH,P0,, 0.4; NaHCO,j 11.9 and glucose, 5.5. The solu tion was saturated with 95% 02 and 5 % CO, mixture and maintained at 37°C. Tension changes were isometrically recorded with a mechanoelectro-transducer.

Effect of Histamine on Calcium Movement in Guinea Pig Taenia Coli

“…on the smooth muscles in the presence of various stimulants and relaxants. However, the presence of the correlation between tension development and the size of TBF has al ready been suggested (3)(4)(5) and the present data also supports this.…”

“…However, as reviewed by L&uuml;llmann (1), no correlation has been found between tissue Ca content or Ca fluxes and the contractile response of the smooth muscle to various stimu lants.<BR> In guinea pig taenia coli, it was shown that cellular Ca fraction of relatively tightly bound form increase during contraction induced by barium or high concentration of potas sium and decreased during the abolition of tension development by various inhibiting factors, and suggested that the shift of Ca into the relatively tightly bound fraction with in the cell might have a concern with the tension development (2)(3)(4)(5).<BR>…”

Effects of ouabain on high-K induced contractions of various smooth muscle tissues in the guinea-pig.

“…Previous studies have shown that the tonic contraction produced by a high-K solution is inhibited by ouabain in the guinea-pig taenia coli (2,(19)(20)(21)(22)(23)(24) and ileum (25). In the present paper, we have found that the effects of ouabain on K-contraction are different in several smooth muscle tissues isolated only from the guinea-pig.…”

The Regulation of Respiration of Guinea Pig Taenia Coli in High-K Medium; The Role of Nicotinamide-Adenine Dinucleotide, Adenosine Diphosphate and Ca++

“…It has been reported that the smooth muscle of guinea pig taenia coli requires the aerobic breakdown of carbohydrate to maintain a continuous tension in a high-K (40 mM) medium (1) and that during the tonic contraction, Ca++ enters across the cell membrane into the muscle (2) and also that both the changes in tension and Ca++ movement induced by the high-K are abolished by an application of 10-4M DNP or anoxia (3). In preliminary work we have found that the inhibitors of NADH oxidation in mitochondrial respiratory chain which have no effect on succinoxidase activity, such as amytal, piericidine A, and rotenone, also abolished the high-K induced tonic tension in the taenia coli.…”