BRONCHIAL SMOOTH-MUSCLE ENERGETICS - EFFECT OF IODOACETATE AND HYPOXIA

The active pressure (AP) and the oxygen consumption (V-O2) of segments of bovine bronchi were measured during a 10 mu M carbachol stimulatio n. V-O2 did not increase during the carbachol-induced contraction wher eas there was a twofold increase in the lactate production. Addition o f the glycolytic blocker, iodoacetate (83 mu M), decreased the AP to 6 8.9 +/- 6.4% of control value (n = 10, P<0.05) whereas V-O2 remained c onstant. The lactate concentration in the physiological solution decre ased significantly (P<0.05). When the solution was supplemented with p yruvate (10 mM), the effect of iodoacetate was antagonized. Under hypo xic condition, i.e. when the solution was bubbled with 5% CO2 in N-2, V-O2 decreased sharply to 7.7 +/- 3.1% of control (n = 8, P<0.05) wher eas AP did not change. The combined effect of iodoacetate and hypoxia led to a fall in both AP (12.4 +/- 3.0% of control, n = 7, P<0.05) and V-O2 (21.2 +/- 5.1%, P<0.05). These results suggest that the energy r equired by bronchial smooth muscle to generate contraction could be su pplied by either the aerobic or the anaerobic pathway.