Effects of Factors Inhibiting Tension Development on Oxygen Consumption of Guinea Pig Taenia Coli in High K Medium

1970

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Previous studies have shown that Ca influx increased but Ca efflux did not change during the contracture of taenia coli induced in hypertonically added 40 mm potassium solution (1) and the results were supported by the others (2-6). Further, the movements of Ca in the muscle in high-K solution might be differently affected by ouabain and 2, 4-dinitrophenol during the abolition of the tonic tension by them (6, 7).The experiments reported here were carried out in purpose to find the nature of Ca distribution and exchange in guinea pig taenia coli in high-K solution using ouabain and 2, 4-dinitrophenol. METHODSStrips of taenia coli isolated from white male guinea pigs were suspended in an organ bath containing Tyrode solution of the following composition (mm); NaCI 136.8, KCl 2.7, CaC1, 2.5, MgCl2 1.0, NaH2PO4 0.4, NaHCO, 11.9 and glucose 5.5, saturated with 95% 02 and 5% CO, mixture at 37'C. Isotonically added 40 mm K solution (iso-40 K-S.) was made by replacing 40 mm NaCI in Tyrode solution with equimolar KC1. Tension changes were isometrically recorded with a mechanoelectro-transducer. 45Ca uptake: After pretreatment , muscle strips were soaked in iso-40 K-S. for 30 minutes, then 2.5 x 10-6 M ouabain or 1 x 10-4 M 2, 4-dinitrophenol (DNP) was added. Thirty minutes after the addition of ouabain or DNP, corresponding to zero time of Fig. 1, 45Ca (1 x 106 counts/min-ml) was added to the medium for incubation. After 5, 15 or 30 minutes incubation period, the strips were removed from the bath and radioactivities in the muscle strips were counted (1, 4). Tissue Ca: Strips were treated in the same manner as that in the preceding para graph except that 45Ca was not used and Ca content of the tissue was determined using atomic absorption spectrophotometer (1, 4). 45Ca efflux: Muscle strips were incubated in iso -40 K-S. with 45Ca (200 pCi/ml) for 180 to 200 minutes and then washed by dipping into successive tubes containing iso

Section: Discussionmentioning

confidence: 62%

Effects of Ouabain and 2,4-Dinitrophenol on Calcium Distribution and Exchange in Guinea Pig Taenia Coli in High-Potassium Solution

Karaki

Ikeda

1970

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“…Pap at 5,,1,10-5 M inhibited the increased Qo2 and tension simultaneously, much the same as was seen with amytal (20). From the series of experiments concerning O2 consumption (20)(21)(22)(23), it is known that in the 40-K medium, the inhibition of increased Qo2 (IQo) is sufficient for the inhibition of developed tension (12e) but is not a necessary condition.…”

Section: It Was Reported Thatmentioning

confidence: 67%

The Inhibitory Effect of Papaverine on Respiration-Dependent Contracture of Guinea Pig Taenia Coli in High-K Medium. I. The Relationship Between Contracture and Respiration

Tsuda¹,

Saitō

1977

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Abstract-Papaverine(Pap) inhibited a tonic tension development in guinea pig taenia coli induced by an elevation of the potassium concentration of the medium to 40 mM The potassium ion is known as a non-selective stimulant for various smooth muscle.The K-contracture of taenia coli showed different metabolic dependences, even in the same K medium, depending on whether the recording was isotonic or isometric (1, 2). In isometric recordings, the K-contracture showed different shapes, metabolic dependencies and Ca move ments varying with the Na-K ratio of the medium and/or the degree of depolarization (3-6).Papaverine (Pap) is well known as a non-selective relaxant of smooth muscle. Pap at 2.5,/'% 10-s M, selectively inhibited the tonic contraction without affecting the phasic one in various types of K-contractures of taenia coli which were induced by 40-K or when high-K was completely substituted for Na, under isometric or isotonic recordings (7-9). Pap possibly induces a dissociation between the electrical and mechanical activity of smooth muscle, both in spontaneously active preparations and in high-K medium (7, 10). The relaxant effect is independent of a direct inhibitory effect on the contractile machinery (11).

“…Saito et al (4) found that an application of the high-K caused an increase in 02 con sumption accompanied by an increase in tension change in the taenia coli, and also that addition of 10-1 M DNP to the high-K medium further increased or maintained the 02 consumption although it abolished that developed tension, and that the change in 02 con sumption was not modified by the Ca++ removal from the medium (5). In light of these results, the possibility of the essential role of ADP in stimulating respiration of the smooth muscle during the tonic tension maintenance and the active Ca++ movement warrants further investigation.…”

mentioning

confidence: 99%

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

Tsuda

Saitō

et al. 1975

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Abstract-In an attempt to elucidate the regulation mechanism of respiration in the smooth muscle cell, we investigated the roles of nicotinamide-adenine dinucleotide (NAD), adenosine diphosphate (ADP) and Ca" in the muscle respiration using the tissues and subcellular fractions from guinea pig taenia coli. The tension in the strips of taenia coli increased with a concomitant increase in 02 consumption in high-K medium (40 mM K) containing 2.5 mM Ca. 10-3 M amytal and 10-6 M ouabain decreased the high-K induced tension and 02 consumption of the muscle. 10-4 M 2,4-dinitrophenol (DNP) relieved the decreased respiration induced by ouabain, but not that with amytal. From these data it is suggested that NADH-linked respiration plays an important role in the respiration of the muscle. Ca++ in concentrations ranging from 0.5 to 2.5 mM in the high-K medium resulted in an increase in tension and in 02 consumption progressively. In spectrophotometric observations of subcellular fractions of the taenia coli, ADP increased in absorbance change at 340 mtg. Such occurred in mitochondrial fractions and was initiated by the addition of NADH. Therefore it is deduced that the increase in ADP level of the cytoplasm is primarily due to a contraction triggered by Ca" thus stimulating respiration. On the other hand, at 0.1 mM of Ca++ concentration, the muscle strip increased O2 consumption without tension development in high-K medium. In the spectrophotometric obser vations, Ca++ and Sr++ increased the absorbance change in the homogenate and in the mitochondrial fraction. Hence, it seems that one part of the Ca++ entering into the smooth muscle treated with the high-K increased O2 consumption in mitochondria independent of an increase in muscle tension. From these results it is concluded that NADH-linked respiration plays an important role in the smooth muscle respi ration in high-K medium and that ADP and Ca++ also play a role in regulating res piration.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