Effects of Chronic Hypoxia on Electrogenic Transport and Transport-related Oxygen Consumption in Rat Distal Colon
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The distal colon epithelium of rats submitted to chronic hypoxia shows higher short-circuit current (I sc) which, unlike non-hypoxic rat epithelium, has an amiloride-sensitive component despite low serum aldosterone levels. I sc and oxygen consumption (QO2) were simultaneously measured in mucosae from rats submitted to 0.5 atm for 10 days and from control rats in a modified Ussing chamber. Hypoxia increased I sc but not QO2. The slope of the regression line between I sc and QO2 reduction after ouabain addition was decreased in epithelia from hypoxic rats (P = 0.03). Chloride secretion blockade reduced I sc and QO2 in both groups, while sodium channel blockade did so only in the hypoxic group. Dual blockade in hypoxic rat epithelia caused correlated (P = 0.0025) additive decreases in I sc and QO2. Presented results suggest that chronic hypoxia induces an improved coupling between QO2 and electrogenic ion transport, and electrogenic sodium absorption despite low aldosterone levels.
KeywordsAldosterone Chronic hypobaric hypoxia Electrogenic sodium transport Oxygen consumption Rat distal colon Short-circuit current
This work was supported by grant 06/J-185 to Fernando D. Saraví and a scholarship awarded to Liliana M. Cincunegui, both from the Universidad Nacional de Cuyo.
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