Transferrin messenger ribonucleic acid: molecular cloning and hormonal regulation in rat Sertoli cells

Transferrin-specific cDNA clones were isolated from a rat liver cDNA library prepared from transferrin-enriched mRNA. Hybrid selection and sequence analysis confirmed that the selected clone contained the carboxy-terminal coding region of the transferrin mRNA. Northern blot analysis was used to demonstrate the presence of transferrin mRNA in liver and Sertoli cells. Transferrin mRNA levels were measured in total RNA isolated from cultured rat Sertoli cells after treatment with FSH, insulin, retinol, and testosterone. The results showed a 2- to 4-fold increase in the level of transferrin mRNA, which peaked on the fourth day of culture after initiation of treatment, with FSH, insulin, retinol, and testosterone. This induction is gene specific, since no change in the mRNA levels for either the catalytic or regulatory subunits of cAMP-dependent protein kinase was observed. The effects of hormones, vitamin A (retinol), and Bu2 cAMP on transferrin mRNA and transferrin secretion (measured by RIA) in cultured Sertoli cells were compared. In general, a direct relationship between the amount of transferrin mRNA present in the cells and the amount of transferrin secreted into the culture medium was observed. These results demonstrate the important role that vitamin A, testosterone, and peptide hormones play in modulating transferrin gene expression in Sertoli cells.