Modification of prolactin receptor (PRL-R) expression by PRL in the mouse liver: estimation of the ratio of two forms of PRL-R mRNAs by "one-sided competitive PCR".

Abstract

We developed new means of measuring the ratio of the short to the long form (S/L ratio) of the mouse prolactin receptor (mPRL-R) cDNA by PCR using a primer common to the two forms and two specific primers. A means of estimating the amount of mPRL-R cDNA by competitive PCR was also established. We confirmed that these procedures were valid, since the S/L ratio of standard DNA was unaltered by one-sided cPCR amplification under the following conditions: the ratio was between 0.1 and 4, and the amount of cDNA was between 10(3) and 10(7) molecules/tube. The result of one-sided cPCR showed that the short form was dominant in the mouse liver, while the long form was dominant in other tissues. In addition, pituitary grafting increased the S/L ratio in the liver, implying that prolactin down-regulated the functional long form of PRL-R and lowered tissue sensitivity to prolactin itself by modifying the post-transcriptional regulation of PRL-R.