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

Abstract

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

On the inhibitory mechanism of bassianolide, a cyclodepsipeptide, in acetylcholine-induced contraction in guinea-pig taenia coli.

“…This effect of papaverine was consistent with that reported in other papers (20,21). Since BASS did not remarkedly inhibit the 60 mM K-induced tonic con traction, the action of BASS seems to be also different from that of papaverine which inhibits phosphodiesterase activity (22)(23)(24) or mitochondorial respiration (25,26).…”

The Inhibitory Effect of Papaverine on Respiration-Dependent Contracture of Guinea Pig Taenia Coli in High-K Medium. Ii. Inhibition of Mitochondrial Respiration

“…The essential role of NAD`.-linked respiration in the smooth muscle respiration in 40-K medium was reported previously (8). Moreover, the inhibition of Pap to the NADH-linked respiration reached a steady level within 1 min in both the homogenate and in the Mt of taenia coll.…”

“…Pigeon heart homogenate was centrifuged for 5 min at 600 x g to produce a supernatant which was centrifuged for 20 min at 12,000 x g to yield the resultant pellet that was centrifuged for 15 min at 5,500 x g. This pellet was used as the pigeon heart mitochondrial fraction. A taenia coli homogenate and Mt were also prepared using the Ultra-Turrax as reported previously (UT method) (8). All procedures were performed at low temperatures (W-4`Q.…”

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

“…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.…”

“…, in each treatment. It was previously reported that the reduction of intracellular Call concentration inhibited both the smooth muscle tension and the muscle respiration, and that the reduction of ATP utilization also inhibited Qo2 (20). However, these inhibitions of Qo2 were fully antagonized by DNP (20).…”