QUANTITATION OF ANDROGEN RECEPTOR MESSENGER-RNA BY COMPETITIVE REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION

A quantitative reverse transcription-polymerase chain reaction (RT-PCR) was developed to study the differential expression of androgen receptor (AR) mRNA. This assay is based on a competitive internal standard (IS-AR) which can be discriminated from AR mRNA by the insertion of an exogenous DNA fragment. The method requires less than 1 mu g total RNA and provides a fast and precise way to quantitate minute amounts of AR mRNA isolated from human and rat tissues. A twofold difference in AR mRNA levels can be detected by this RT-PCR method. Based on RT-PCR quantitation, the relative expression of AR mRNA (using prostate as 100%) in 28 tissues from five Sprague-Dawley female rats (indicated as *) and the same number of males was as follows: hypothalamus (217%* vs 42%), adrenal gland (186%* vs 141%), epididymis (115%), thyroid gland (68%), Harderian gland (58%), pituitary gland (56% vs 9%*), preputial gland (44% vs 38%*), quadriceps muscle (35%), levator ani muscle (30%), kidney (27% vs 7%*), coagulating gland (25%), seminal vesicle (25%), testis (20%), liver (18% vs 9%*), submaxillary gland (17%), bulbocavernosus muscle (16%), vagina (9%*), heart (8% vs 7%*), ovary (4%*) and uterus (2%*). Lower values were found in other tissues such as sublingual gland, stomach, lung, cervix*, lacrimal gland, spleen and diaphragm ranging from 0.8%-0.2%. These data suggest that high levels of AR mRNA expression are not limited to male reproductive organs. Also, sexual dimorphism exists in the AR mRNA level in diverse rat tissues as determined by RT-PCR.