title: 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.
abstract: The differential effects of papaverine (Pap) and rotenone (Rot) were studied on the highly respiration-dependent contracture of guinea pig taenia coli in 40 mM potassium (40-K) medium, on isolated DT diaphorase activity and on mitochondrial respiration. The inhibition of guinea pig taenia coli to the 40-K induced tension by Rot (5 x 10(-7)M) was fully reversed by the addition of a water soluble vitamin K3 (VK3) derivative or menadione sodium bisulfite (MSB). A low concentration (10(-7)--10(-6)M) of Pap which had no effect on the 40-K induced tension inhibited the VK3 restored tension from the Rot suppression, corresponding to a Pap inhibition of the isolated DT diaphorase. Inhibition of the effective concentration of Pap to the 40-K induced tension development was never reversed by addition of VK3 or MSB. In taenia coli, both MSB and VK3 established a bypass of the Rot sensitive site on the mitochondrial respiratory chain by means of the DT diaphorase system. The difference in washout-efficacy between Pap and Rot on the inhibition of 40-K induced tension was ascribed to a difference in their mitochondrial binding properties.
mesh_terms: D000818:Animals; D003106:Colon / Q000187:drug effects; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008928:Mitochondria / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects*; D010208:Papaverine / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D011808:Quinone Reductases / Q000378:metabolism*; D051381:Rats; D012402:Rotenone / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D014812:Vitamin K / Q000494:pharmacology
chemical_list: D012402:Rotenone; D014812:Vitamin K; D010208:Papaverine; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D011188:Potassium