Coated pits and coated vesicles in the endothelial cells of trabecular meshwork.

Coated pits (CPs) and coated vesicles (CVs) were investigated in the trabecular meshwork of man and rabbit. In both man and rabbit CPs and CVs appear to be randomly distributed throughout the trabecular tissue. CVs are located in the peripheral cytoplasm of the trabecular endothelial cells and show an average diameter of 0 . 16 micron. The ratio between the number of CPs and CVs ranges from 0 . 53 (rabbit) to 0 . 6 (man). The number of CPs and CVs is higher in rabbit than in man. Consequently, the overall CPs surface and CVs volume density estimates are higher in rabbits, where CPs represent about 1% of the cell surface and CVs account for about 0 . 4% of the cell cytoplasm. In man these percentages are 0 . 46 and 0 . 17%, respectively. No significant changes of CPs and CVs were found in rabbits with corticosteroid-induced ocular hypertension. However, changes in length of boundary membrane of CPs, though not statistically significant, were accompanied by proportional changes in CVs diameter.