Quantitative studies of rat carotid body type I cells.

The general structure and results of quantitative studies of rat carotid body type I cells are described. In contrast to previous reports, there was no change in mitochondrial V/v% on stimulating the carotid body with 10% oxygen. The volume of cytoplasm occupied by electron-dense cored vesicles was significantly increased, whilst their density per square micrometre of cytoplasm was decreased during hypoxia. Thus, the size of vesicles is increased by hypoxic stimulation. On the basis of vesicle diameter and density we were unable to find evidence of more than one variety of type I cell.