Hepatic expression of rat P450 mRNA assessed by in situ hybridization to oligomer probes.
Cell-specific chemical toxicities may be influenced by P450-catalyzed biotransformation reactions. We have undertaken an analysis of P450 expression in isolated rat liver sections to assess better the cellular distribution of P450 gene products. Discriminatory 18-mer oligodeoxynucleotides directed to the phenobarbital (PB) inducible P450s, P450IIB1 (P450b) and P450IIB2 (P450e), were employed as probes for in situ hybridization experiments. With these techniques we demonstrate that P450b and P450e mRNAs are each expressed in the hepatic lobule with similar spatial distribution. In animals pretreated with PB, only cells within the immediate periportal region were refractory to induction. Based on autoradiographic grain densities, responsive hepatocytes accumulated P450b mRNA at levels exceeding that for P450e. We employed in situ hybridization methodology in combination with Northern blot analyses to compare the expression of these mRNAs in two rat strains, Sprague-Dawley and Marshall 520/N (the latter being deficient in the synthesis of P450e isozyme; Rampersaud and Walz, 1987). These strains provided valuable comparative models, demonstrating the specificity and sensitivity of the oligomer probes. The continued development of in situ hybridization methodologies, especially when used in conjunction with synthetic oligomer probes, will permit a detailed analysis of P450 expression in different tissues, under a variety of chemical exposures, and may be a valuable adjuvant to the prediction of target organ toxicities.
Hassett
C
C
Department of Environmental Health, School of Public Health and Community Medicine, University of Washington, Seattle 98195.
Luchtel
D L
DL
Omiecinski
C J
CJ
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D015345:Oligonucleotide Probes; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D011919:Rats, Inbred Strains
D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System