Retinoid metabolism in spontaneously transformed mouse fibroblasts (Balb/c 3T12-3 cells): Enzymatic conversion of retinol to anhydroretinol

Spontaneously transformed mouse fibroblasts (Balb/c 3T 12-3 cells) displayed an increased adhesion when cultured in the presence of 10 ^-6 M all trans retinol and acquired morphological characteristics of the normal phenotype. Thus it was of interest to investigate the metabolism of [15- ¹⁴C] retinol in this system. Within 24 hours of culture, approximately 4.25% of the [ ¹⁴C]retinol was taken up by the cells. The hydrocarbon [ ¹⁴C]anhydroretinol was a major metabolic product and was identified by gas liquid chromatography and by its typical ultraviolet absorption spectrum with maxima at 386, 364, and 346 nm. At 24 and 40 hours anhydroretinol represented 27% and 55%, respectively, of the total nonpolar metabolites or approximately 16% and 30% of the total radioactive products. Formalin fixed fibroblasts or cultured intestinal mucosal cells did not convert retinol into anhydroretinol. A more polar product with a UV absorption maximum at 310 nm was also found. The time course of the synthesis of this product by 3T12 cells suggested a precursor product relationship with anhydroretinol. A microsomal preparation from 3T12 cells was also active in synthesizing [ ¹⁴C]anhydroretinol and [ ¹⁴C]metabolite 310 from [ ¹⁴C]retinol. Moreover incubation of metabolite 310 with the 3T12 microsomes yielded anhydroretinol (40% conversion in 30 minutes), suggesting that metabolite 310 is an intermediate in the synthesis of anhydroretinol by these cells. Anhydroretinol appears to be an end product of the metabolism of retinol 3T12-3 cells, as suggested by the findings that over 90% of [ ¹⁴C]anhydroretinol incubated for 30 hours with 3T12-3 cells was recovered unaltered, without the formation of detectable retroretinol, retinol, or retinoic acid.