Hypoxia stimulates endothelial cell angiotensin-converting enzyme antigen synthesis.
Previous studies from our laboratory indicate that exposure of the rat to chronic normobaric hypoxia reduces stores of active angiotensin-converting enzyme (ACE) in the lung. This study assesses directly the effects of hypoxia on ACE synthesis in cultured porcine pulmonary artery endothelial cells. Confluent cultures were exposed to hypoxia [2.5% O2 at 1 atmosphere (atm)] in a triple gas incubator; controls were cultured in normoxic conditions. After 24-, 48-, and 72-h exposure to hypoxic or normoxic conditions, followed by incubation with [35S]methionine for an additional 24 h under the same conditions, newly synthesized radiolabeled ACE was quantitated. Radiolabeled ACE was isolated by an immunobead procedure using either anti-ACE (porcine lung) immunoglobin G (IgG) or nonimmune IgG. A single radiolabeled peak (150 kDa) with the same electrophoretic mobility as purified porcine lung ACE was observed. There was a significant time-dependent increase in endothelial cell ACE antigen synthesis without a concomitant change in either cell number or total trichloroacetic (TCA)-precipitable protein in hypoxic cells compared with normoxic controls. In contrast, ACE activity, assessed by conversion of 125I-labeled angiotensin I to 125I-labeled angiotensin II was unchanged in cultures exposed to hypoxia (2.5% O2). This suggests that an inactive form of ACE is synthesized by cultured pulmonary artery endothelial cells under hypoxic conditions.
King
S J
SJ
Department of Medicine, University of Alabama, Birmingham 35294.
Booyse
F M
FM
Lin
P H
PH
Traylor
M
M
Narkates
A J
AJ
Oparil
S
S
D000693:Anaerobiosis; D000818:Animals; D000936:Antigen-Antibody Complex; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000201:enzymology*; D000860:Hypoxia / Q000201:enzymology*; D007074:Immunoglobulin G; D008970:Molecular Weight; D007703:Peptidyl-Dipeptidase A / Q000096:biosynthesis* / Q000302:isolation & purification; D011651:Pulmonary Artery / Q000201:enzymology
D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D007703:Peptidyl-Dipeptidase A