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

Abstract

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).

The Inhibitory Effect of Papaverine on Respiration-Dependent Contracture of Guinea Pig Taenia Coli in High-K Medium. Iii. The Differential Effect of Papaverine and Rotenone on Dt Diaphorase

“…Rot at low concentrations is a highly specific inhibitor of NADH oxidation (6). In the present work, we confirmed the previous proposal (1,5) that Pap inhibits the 40-K induced tonic tension by a direct inhibition of mitochondrial respiration, by using a comparison of Rot and its effects on tension, on the Present Address: Laboratory of Pharmacology, Toxicology Division, The Institute of Environ mental Toxicology, Kodaira-shi, Tokyo 187, Japan isolated DT diaphorase and on the respiration of mitochondria pretreated by the drugs.…”

Inhibition by papaverine of calcium movements and tension in the smooth muscles of rat vas deferens and urinary bladder.

“…Tsuda et al (1977) explained papaverine inhibition of K-induced tension in guinea-pig taenia coli in terms of inhibition of mitochondrial respiration. K depolarization does stimulate muscle fibre respiration (Van Der Kloot, 1967) but respiratory inhibition seems unlikely to be a factor in the experiments reported here.…”

“…Similarly in the non-spontaneous smooth muscle ofguinea-pig ureter papaverine does not affect membrane potential but it does reduce the plateau response and associated spikes evoked by depolarization (Brading, Burdyga & Scripnyuk, 1983). Tsuda, Urakawa & Saito (1977) noted that papaverine inhibited the tonic phase of K contractures in guinea-pig taenia coli, which they ascribed to inhibition of mitochondrial respiration.…”

Effects of Papaverine on Twitches in Mouse Diaphragm

“…Tsuda et al [6][7][8] showed that papaverine inhibited high K + -induced contraction and O 2 consumption in guinea pig taenia coli and inhibited mitochondrial respiration by blocking the transduction of electrons between NADH and coenzyme Q and by inhibiting NADH and NADHP-diaphorase. Conversely, Ozaki et al [38] reported that the high K + -induced contraction was accompanied by an increase in FPox fluorescence or PNred fluorescence in guinea pig taenia coli.…”