ELECTRON MICROSCOPIC STUDY OF ACID PHOSPHATASE ACTIVITY IN CULTURED HUMAN CYSTIC FIBROSIS FIBROBLASTS

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Electron microscopic localization of acid phosphatase (ACPase) activity was investigated in cultured human fibroblasts from cystic fibrosis homozygotes and heterozygotes and from normal subjects using the Teflon-treated coverglass method (8). Our data suggest the following: 1) ACPase activity was found in lysosomes, in strikingly well-developed Golgi complexes and occasionally in rough endoplasmic reticulum (RER), irrespective of cell lines. 2) The ACPase activity of the Golgi complex was localized in the cisternal portions arranged in parallel and also in the thick reticular portions which may correspond to the GERL (20). 3) No clear-cut differences were observed in the localization or in the intensity of the ACPase activity among cells from cystic fibrosis homozygotes and heterozygotes and from normal subjects. 4) Cells in the confluent stage showed a tendency to have more lysosomes and less-developed Golgi complexes than those in the preconfluent stage. 5) The increase in the lysosome number in the confluent stage is mainly due to the change of the characteristic membrane-bounded bodies into secondary lysosomes. 6) RER may directly supply ACPase to secondary lysosomes during their formation.