Abstract
Hepatic heme metabolism and in vitro translation of poly(A) + RNA from livers were studied to elucidate the mechanism of the reduction of microsomal cytochrome P-450 in tumor-bearing mouse livers. Hepatic delta-aminolevulinic acid synthase activity in male C57BL/6N mice (0.203 nmol/mg protein/h) at 8 days after the transplantation of Ehrlich ascites tumor cells was the same level as that of normal livers (0.206 nmol/mg protein/h). On the other hand, hepatic heme oxygenase activity of tumor-bearing mice (0.482 nmol/mg protein/10 min) had increased 8 days following i. p. transplantation of tumor cells when compared with that of normal mouse livers (0.296 nmol/mg protein/10 min). SDS-gel electrophoresis of in vitro translation products of poly(A) + RNA extracted from membrane-bound polysomes of the livers from tumor-bearing mice showed no significant differences from that of normal controls in the region of cytochrome P-450, that is, the molecular weight region of Mr = 47,000-60,000, although microsomal protein content in this region estimated by Coomassie-blue staining was reduced. These results suggest that the decrease of heme biosynthesis or the translation of cytochrome P-450 mRNA played a very small part in the reduction of microsomal cytochrome P-450 in tumor-bearing mice.
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