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

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Abstract
The differential effects of papaverine (Pap) and rotenone (Rot) were studied on the highly respiration-dependent contracture of guinea pig tenia coli in 40 mM K (40-K) medium, on isolated DT diaphorase activity and on mitochondrial respiration. The inhibition of guinea pig tenia coli to the 40-K induced tension by Rot (5 .times. 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 tenia coli, 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.