Abstract
Hypoxia inhibits converting enzyme (CE) activity in vivo in dogs (Fed. Proc. 36:630, 1977). To study the cellular basis of this phenomenon, we harvested endothelial cells by perfusing human umbilical cords, rabbit and pig lungs and calf aortas with a mixture of 0.1% collagenase, 0.1% trypsin and 1.0% chicken serum in Hank's Solution, and propagated the cells in medium 199. CE activity in monolayer cells was assessed by adding both bradykinin and angiotensin I to culture flasks and measuring residual peptide over time by radioimmunoassay. CE activity was fully inhibited by SQ20881. Flasks were equilibrated with varying hypoxic gas mixtures. Hypoxia rapidly inhibited CE activity (< 2 minutes) and room air rapidly restored it (< 2 minutes). All CE activity was inhibited at PO2 of 30 mm Hg. In all species, the extent to which CE was inhibited was a direct function of PO2 (r = 0.99, p < .001). The velocity of the reaction, calculated from 0 to 4 minutes of incubation, was 5.4 nmoles/hr/106 cells when PO2 = 100, 1.6 at PO2 = 50, and <0.11 at PO2 = 30. Commercial purified pig converting enzyme was unaffected by hypoxia (VMAX = 2.2 nmoles/mg protein/hr at all P02 levels from 100 to 0 mm Hg). We conclude that the inhibition of CE by hypoxia 1) takes place at the cellular level and 2) is not a characteristic of the enzyme per se but is a unique property of the endothelial cell membrane.
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Stalcup, S., Lipset, J., Woan, J. et al. 1233 EFFECT OF ACUTE HYPOXIA ON CONVERTING ENZYME ACTIVITY IN CULTURED ENDOTHELIAL CELLS. Pediatr Res 12 (Suppl 4), 569 (1978). https://doi.org/10.1203/00006450-197804001-01239
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DOI: https://doi.org/10.1203/00006450-197804001-01239
