title: Phenotypically selective promotion of diethylnitrosamine-initiated altered hepatocyte foci by dietary phenobarbital or a topically applied coal-derived organic mixture in male and female rats.
abstract: Relative frequencies of diethylnitrosamine (DEN)-initiated foci of altered hepatocytes appearing in response to promotion by either dietary phenobarbital or a topically applied coal-derived organic mixture (CDM) were investigated in male and female rats. The focus population was examined for two histochemical markers, elevated gamma-glutamyl transpeptidase [GG(+)] and iron exclusion [FE(-)], giving rise to 3 detectable focus phenotypes, i.e., GG(+) foci, FE(-) foci, and GG(+)/(FE(-) foci. Frequencies of the 3 phenotypes were quantitated through the use of serial frozen sectioning and computer-assisted image analysis. In agreement with our prior observations, cutaneous exposure to CDM or dietary phenobarbital promoted the expression of DEN-initiated foci. However, the current data showed that this promoting effect of CDM occurred only in females and was restricted to foci with the GG(+)/FE(-) phenotype. Dietary phenobarbital, on the other hand, promoted both the GG(+) and GG(+)/FE(-) phenotypes and was effective in both males and females, although a sex-related differential in the promoting efficiency of phenobarbital was also observed. The pronounced heterogeneity in the responses of the 3 focus phenotypes suggests that each phenotype is the consequence of a specific type of genomic alteration with a specific capacity to undergo phenotypic expression in response to a given promoting stimulus.
mesh_terms: D000287:Administration, Topical; D000818:Animals; D003031:Coal; D003043:Cocarcinogenesis; D005260:Female; D007501:Iron / Q000032:analysis; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced*; D008297:Male; D010634:Phenobarbital / Q000633:toxicity*; D010641:Phenotype; D011230:Precancerous Conditions / Q000139:chemically induced*; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D013045:Species Specificity; D005723:gamma-Glutamyltransferase / Q000032:analysis
chemical_list: D003031:Coal; D007501:Iron; D005723:gamma-Glutamyltransferase; D010634:Phenobarbital