Freeze-etching images of rabbit thyroid glands.

Freeze-etching images of the rabbit thyroid were described. The outline of the structure of the follicular epithelial cell in freeze-etching techniques is consistent with that in ultrathin sections. The subapical junctional complex consists of tight and gap junctions. According to the number of strands (5-16) indicating the tight junction and the depth of the tight junction (0.3-1.1 mum), this is classified into the "very tight" form of CLAUDE and GOODENOUGH(1973). The number of intramembranous particles per mum2 on the A-face of the lateral as well as the apical plasma membrane is far larger than that on the B-face. The limiting membrane of the reabsorbed colloid droplet shows also a similar pattern to that of the plasma membrane. The capillary endothelial cells show numerous fenestations whose population density is about 20/mum2 on the endothelial surface except in the parajunctional zone.