Ion transport, Oxygen consumption.

Chronic hypobaric hypoxia is a physiological environ-mental stressor. While its effects on most major organ systems have been extensively studied, few works have addressed hypoxia-induced changes in intestinal trans-port. The effects of cyclooxygenase blockade with indo-methacin on short-circuit current (Isc) and oxygen con-sumption (QO2) of the distal colonic epithelium of control rats and rats submitted to hypoxia for 10 days at 0.52 atm were studied. Isolated mucosae were mounted in an Ussing chamber modified for measu-ring QO2 while preserving transepithelial vectorial transport. Amiloride was added to the mucosal hemi-chamber to block a sodium component of Isc present in hypoxic rats. In this condition, basal Isc did not differ between the hypoxic and the control group, but QO2 was higher in the former. Indomethacin (30 µmol/L) reduced Isc to the same extent in both groups, but QO2 reduction was larger in the hypoxic group. Pharmaco-logical blockade of chloride secretion and a low-chlori-de solution abolished the indomethacin-induced reduc-tions of Isc in both groups, and the reduction of QO2 in controls, and attenuated but did not suppress the QO2 reduction in the hypoxic group. Linear regression analysis of QO2 changes versus Isc changes yielded a significant correlation for both groups, with regression lines with the same slope, but a higher position in hy-poxic animals. Results suggest that spontaneously relea-sed prostaglandins are equally important for maintai-ning colonic chloride secretion in hypoxic as in normo-xic rats, but that, in the former, indomethacin has an additional effect on QO2 which is unrelated to ion transport