Quantitative analysis of growth hormone (GH) pre-mRNA expression in cultured rat anterior pituitary cells by an intron-specific and competitive PCR method.

We have developed a novel method of quantifying growth hormone(GH) pre-mRNA expression in anterior pituitary cells. DNA-free total RNA extracted from cultured rat anterior pituitary cells was reverse transcribed(RT) to cDNA, and RT products were subsequently quantitated by competitive PCR using intron-specific primers of rat GH gene. After 6-h of incubation in treated cells, dexamethasone(Dex) and triiodo-L-thyronine(T3) significantly increased GH pre-mRNA levels(3.2- and 2.2-fold compared to non-treated cells, respectively). However, Northern blot analysis did not detect significant changes in GH mRNA levels. After 24-h incubation with Dex and T3, significant increases in GH mRNA levels were detected on Northern blots, but GH pre-mRNA levels did not differ between treated and non-treated cells. These findings suggest that both Dex and T3 treatments rapidly increase GH pre-mRNA levels in normal somatotropes. This method has high sensitivity and widespread application to the analysis of pre-mRNAs of target genes.