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 recep tor (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 RN A and provides a fast and precise way to quantitate minute amounts of AR mRNA isolated from human and rat tissues. A twofold difference in A R mRNA levels can be detected by this RT-PCR method. Based on RT-PCR q uantitation, 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 4 2%), adrenal gland (186% vs 141%), epididymis (115%), thyroid gland ( 68%), Harderian gland (58%), pituitary gland (56% vs 9%), preputial g land (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%), bulbocaver nosus muscle (16%), vagina (9%), heart (8% vs 7%*), ovary (4%*) and u terus (2%). Lower values were found in other tissues such as sublingu al gland, stomach, lung, cervix, lacrimal gland, spleen and diaphragm ranging from 0.8%-0.2%. These data suggest that high levels of AR mRN A expression are not limited to male reproductive organs. Also, sexual dimorphism exists in the AR mRNA level in diverse rat tissues as dete rmined by RT-PCR.