Some findings on the cytochemistry of the thyroid follicle epithelial cell in rats and mice.

The fine structural localization of endogenous peroxidase was studied in follicle epithelial cells of the rat thyroid. The localization of thiamine pyrophosphatase (TPPase) and acid phosphatase (AcPase) as well as the result of long time osmium impregnation in thyroid follicle epithelial cells were examined in the mouse. All the subapical secretory granules are principally peroxidase-positive, while the reabsorbed colloid droplets are almost peroxidase-negative. In addition, the cisternae of the rough endoplasmic reticulum, the nuclear envelope, 1-3 lamellae on the trans-side of the Golgi apparatus, rigid lamellae, and small vesicles on the trans-side of the Golgi apparatus, and the peripheral part of the follicle lumen are usually positive for endogenous peroxidase activity. The Golgi lamellae of the cis-side are very weakly positive. The TPPase activity is localized in 1-3 lamellae and vesicles on the trans-side of the Golgi apparatus and sometimes in rigid lamellae, while the AcPase activity is in 1-3 lamellae and smooth or coated vesicles on the trans-side of the Golgi apparatus, rigid lamellae, lysosomes and some colloid droplets. The areas positive for both enzyme activities are fairly well overlapped. Functional heterogeneity in the Golgi lamellae is suggested by the fact that TPPase, AcPase and endogenous peroxidase activities are limited on the trans-side of the Golgi apparatus, while osmium tetroxide stains only the cisternae of 1-2 lamellae on the cis-side of the Golgi apparatus. From these findings, GERL can be considered a part of the Golgi apparatus and not independent from this organelle in the thyroid follicle epithelial cell.