Freeze-fracture study of the carotid body.

Replicas of freeze-fractured rat carotid body chief (Type I) cells reveal the normal complement of cytoplasmic organelles. En face fractures of the chief cell plasmalemma exhibit occasional sites of fusion of the amine-containing vesicles which characterize the carotid body. The endothelial cells lining the capillary network of the carotid body display numerous pinocytotic vesicles often oriented in linear arrays, and occasional fenestrae. The endothelial cells are joined together by tight junctions which appear as grooves (B face) forming a continuous network over the membrane.