Prolactin cells of female rats treated with the carcinogen 7,12-dimethylbenz(A) anthracene (DMBA) in vivo. An ultrastructural study.

Pituitary prolactin (PRL) cell microadenomata developed in females of a strain of Sprague-Dawley rats (SD1) following intragastric treatment with the carcinogenic hydrocarbon 7,12-dimethylbenz(a) anthracene (DMBA). Similar treatment of another strain of Sprague-Dawley rats (SD2) resulted in mammary tumour development but no PRL cell microadenomata. In SD1 strain rats morphologically distinct populations of PRL cells appeared after DMBA treatment, one composed of cells characterised by abundant, organised but very dilated RER and with large hormone storage granules, 500-600 nm in diameter (P1). The other cell type had electron-dense cytoplasm, narrow organised arrays of RER and moderately large, pleomorphic granules (P2). Both cell types appeared active with large Golgi and prominent nucleoli. P2 cells were most numerous 2 months after DMBA treatment but had virtually disappeared at 6 months and microadenomata were common at 8 months. PRL cells of SD2 rats were uniform in morphology, characterised by only moderate accumulations of RER, pleomorphic hormone storage granules, large Golgi and prominent nucleoli, and showed no close resemblance to either P1 or P2 cells of SD1 strain rats. It is possible that the morphological variations which developed in SD1 PRL cells may represent changes in responsiveness to factors controlling PRL cell secretion and proliferation and which may be pertinent to microadenoma development.

An ultrastructural study of alkaline phosphatase in a transplantable rat osteogenic sarcoma.

Alkaline phosphatase (AP) has been demonstrated by combined electron microscopy and histochemistry in a transplantable rat osteogenic sarcoma, using a modified Gomori technique (Salomon, 1974). During the early stages of growth of subcutaneously implanted tumors, AP was detected in intracellular membrane systems resembling Golgi and on membranes of cells and matrix vesicles. During growth of the tumor, there was extensive development of intercellular collagen, and AP was demonstrated in bodies associated with collagen. In some cases the AP-containing bodies resembled matrix vesicles, but there was considerable size heterogeneity of the AP-containing bodies, suggesting that there may be heterogeneity of matrix vesicles. The amount of detectable AP seemed to increase in all areas of the tumor which were viable, during tumor growth, but no AP could be detected in cell debris of necrotic areas of the tumor (area C) nor associated with collagen in that area. Area D, particularly during later stages of tumor growth, showed the greatest development of calcium deposits, with calcium spicules apparently associated with AP-containing bodies on both cell membranes and collagen. AP-containing bodies also appeared in large numbers in venules during later stages of tumor growth, associated with an amorphous material. This may account for the increase in serum AP activity which occurs during later stages of growth of transplanted tumors. The sites of AP activity in this osteogenic sarcoma were similar to those described in normal tissue, but generally seemed to be more abundant.