Exposure to hypoxia (0% O2) for 4-24 h resulted in increased intracellular L-arginine content and increased activity of calpain, a calcium-dependent neutral cysteine protease, in pulmonary artery endothelial cells. Calpain-inhibitor I abolished the increased L-arginine content in hypoxic cells. When endothelial cell proteins were labeled with [3H]-L-arginine and the cells exposed to hypoxia, we observed an increase in free [3H]-L-arginine and a decrease in [3H]-L-arginine-labeled proteins. Once again, calpain-inhibitor I prevented the increases in free [3H]-L-arginine and the decreases in [3H]-L-arginine-labeled proteins in hypoxic cells. Hypoxia also inhibited the synthesis of L-arginine-containing proteins. Thus, the increase in intracellular L-arginine content in hypoxic pulmonary artery endothelial cells is caused by an increase in proteolysis secondary to calpain and a decrease in protein synthesis. These results indicate that hypoxia can modulate the availability of free intracellular L-arginine, the exclusive precursor of nitric oxide (NO) and the primary substrate of NO synthase, by affecting the synthesis and degradation of cellular proteins.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Cellular Physiology|
|State||Published - May 1996|
ASJC Scopus subject areas
- Clinical Biochemistry
- Cell Biology