The effect of chronic hypoxia on the number and nuclear diameter of type I cells in the carotid bodies of rats.

We measured the number and nuclear diameter of type I cells in the carotid bodies of 10 normal rats and in 10 rats living in a hypobaric chamber at a pressure of 460 mm Hg for 25 to 96 days. In normal rats, the number of type I rats, the number ranged from 15.92 to 30.77 times 10-3 with a mean of 40.79 times 10-3 which differed significantly from that in the control group. In 5 hypoxic rats the number of type I cells was less than the highest figure in the control group. The mean diameter of the nuclei of type I cells of hypoxic rats (5.5 mu) was greater than that of the controls (5.0 mu). The largest type I nuclei were seen in those rats which had been subjected to hypoxia for the shortest time.