Cytoplasmic vacuoles induced during transformation of cells by Bryan strain Rous sarcoma virus (RSV-BH) have been studied using the cationic dye, neutral red (NR). Both the rate of uptake and the accumulation of NR are greater in RSV-BH transformed cells than non-transformed cells. However, uptake was greater in vacuolated than in non-vacuolated cells, whether or not they were transformed. The NR was incorporated into pre-existing vacuoles in the absence of cytoplasmic staining, suggesting the existence of direct channels from the cell surface to the vacuoles. Other low mol. wt. cationic dyes could also be incorporated into vacuoles, although those with branched structures or cationic weights greater than 330 were excluded. No anionic dyes were incorporated.

Infection of cells with a virus mutant, RSV-BH-Ta, induces temperature-dependent vacuolization. After a shift to the vacuole-permissive temperature, vacuoles developed at different rates and with morphological variations with different cations. Vacuoles which had formed in the presence of several cations, (K, Rb, tris, choline) failed to disappear when cells were incubated at a temperature sufficient to revert vacuoles formed in Na-containing medium. No short-term effects of Cl replacements (Br, I, or SO ) on vacuolization or reversal were observed.

The results suggest that these vacuoles are organelles involved in cation uptake. A possible function for these organelles in RSV-BH induced malignancy is discussed.


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