Sustained hypoxia-induced proliferation of carotid body type I cells in rats.

Sustained hypoxia (SH) has been shown to cause profound morphological and cellular changes in carotid body (CB). However, results regarding whether SH causes CB type I cell proliferation are conflicting. By using bromodeoxyuridine, a uridine analog that is stably incorporated into cells undergoing DNA synthesis, we have found that SH causes the type I cell proliferation in the CB; the proliferation occurs mainly during the first 1-3 days of hypoxic exposure. Moreover, the new cells survive for at least 1 mo after the return to normoxia. Also, SH does not cause any cell death in CB as examined by the terminal deoxynucleotidyl transferase-mediated dUTP-X nick-end labeling assay. Taken together, our results suggest that SH stimulates CB type I cell proliferation, which may produce long-lasting changes in CB morphology and function.