Differential expression of thyrotropin hormone genes by GH3 cells and the normal rat pituitary

RNAs from GH3 cells, a rat clonal cell line, and anterior pituitaries of normal rats have been isolated and assayed for the presence of transcripts coding for the alpha- and beta-subunits of thyrotropin hormone (TSH) by hybridization to their respective cDNAs. Northern analysis indicated that GH3 cells lack both TSH transcripts, and that normal anterior pituitary cells contain mRNA for both the alpha- and beta-subunits approximating 800 and 700 nucleotides, respectively. An examination of the DNAs from GH3 cells and normal anterior pituitary tissue revealed no organizational difference when the restriction digests were subjected to Southern analysis. The lack of TSH secretion by GH3 cells is probably not due to sequence modification of genomic DNA, but to undetermined factors controlling transcription.