| Abstrakt: |
The morphology of livers of Wistar rats treated with beta-carotene (BC), vitamin A (VA, retinol acetate) or corn oil (CO, controls) and submitted to the resistant hepatocyte model of carcinogenesis was studied. Preneoplastic lesions (PNL) were smaller and less numerous in the BC group. The latter group also presented fewer placental glutathione-Stransferase (GST-P) positive and hematoxylin and eosin (H&E) distinguishable PNL, with smaller mean areas and smaller mean areas of the liver occupied by PNL. Clear cell foci predominated in BC livers. In picrosirius-stained liver sections, fibrosis, whether or not accompanying the bile ductular cells, surrounded only 16.67% of PNL in the BC group, as compared to 35.71% in the VA group and 87.72% in the CO group. Moreover, the ductular cell reaction was smaller in the BC group. Smooth muscle actin-positive cells surrounded some PNL, mostly in CO rats, and less frequently in the VA and BC groups. Examination by transmission electron microscopy (TEM) showed that cells with nuclei similar to those of perisinusoidal cells, devoid of cytoplasmic fat globules, probably represented myofibroblasts derived from Ito cells and accompanied the ductular cell reaction. On the basis of these results, we suggest that BC reduced not only the PNL but also the ductular (oval) cell reaction in this experimental model. |
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