Down-regulation by progesterone of CFTR expression in endometrial epithelial cells: a study by competitive RT-PCR

To determine the effect of progesterone on the CFTR mRNA level in glandular epithelial cells of guinea-pig endometrium, a competitive RT-PCR was developed using an an internal standard a competitor with the same sequence as CFTR RNA except for a 20 nucleotide insertion. Using this method, the results showed that the CFTR mRNA level decreased in cells treated with estradiol plus progesterone compared to cells receiving estradiol alone. The decrease in CFTR mRNA level was maximal at 12 h incubation and was 27.3% of the CFTR mRNA level in estradiol-treated cells. The effect of progesterone was mimicked by the progestagen, R5020 and was inhibited by antiprogestins, RU 38,486 and ZK 98,299. Results are discussed in relation to the changes taking place in the endometrium in preparation for implantation of the embryo.