Energy Turnover in Resting Muscle

The energy turnover associated with contraction can be divided into several components, more or less interrelated. The most obvious division is in resting and activated energy turnover, where typically the activated is two to three times the resting value in living smooth muscle. Subtracting the resting from the 

FIGURE 3 Microelectrode recordings from two portal veins incubated with p-hydroxybutyrate but no carbohydrate substrate. Upper control lower with 10 M glibenclamide. Arrows mark addition of 2mM cyanide. From Lydrup et al. (1994). 

FIGURE 4 O2 (upper) and force (lower) recordings from an a-toxin-permeabilized guinea pig ileum strip incubated in a closed chamber with a polarographic electrode (cf. Hellstrand and Paul, 1983). Solutions contain PCr (12 mM) and MgATP (3.2 mM). Pyruvate (10 mM) -I- malate (5 mM) added as indicated. Arbitary units. Numbers above O2 record show O2 consumption (background subtracted) relative to first period after addition of pyruvate -1- malate. 

1991 Picher etal, 1994). This ATPase could be substantially ( 70% in rabbit portal vein) reduced by pretreatment of the preparation by the ectonucleotidase inhibitor 4,4 -diisothiocyanatostilbene-2,2 -disulfonic acid (DIDS), followed by inclusion of sodium azide in solutions used for permeabilized preparations. This treatment dramatically reduced the ADP/ATP ratio measured in permeabilized muscle and increased contractile force. This method may greatly improve the usefulness of a-toxin-permeabilized preparations for energetics studies. 

Time Course of Energy Turnover during Contraction 

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