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"

Expression of prolactin messenger ribonucleic acid in the mouse gonads during sexual maturation

The pituitary hormone prolactin is known to be produced in various extrapituitary tissues as well. We examined the presence of prolactin mRNA in the mouse gonads by reverse transcription (RT)-PCR and nucleotide sequence analysis. Both ovary and testis were found to express small amounts of mRNA coding prolactin, identical to that in the pituitary gland. Next, we established a sensitive competitive RT-PCR method to estimate the amount of prolactin mRNA and then measured its expression in the gonads during sexual maturation (10-80 days of age). In the ovary, the amount of prolactin mRNA (copies/microg of total RNA) gradually decreased from day 10 to 40, and the lower level was maintained until day 80. Little difference in the amount was observed between the estrous and diestrous groups on day 80. Conversely, the amount of testicular prolactin mRNA gradually increased from day 10 to 80. These results suggest that prolactin is produced in the mouse gonads and that it acts as an autocrine/paracrine factor modulating gonadal functions.

Ovarian steroids differentially regulate the expression of PRL-R in neuroendocrine dopaminergic neuron populations: a double label confocal microscopic study

The aims of this study were (1) to identify the possible hypothalamic targets for a short prolactin (PRL) feedback in the adult female rat by identifying DAergic neuron populations expressing PRL receptor (PRL-R); (2) to describe the effect of ovarian steroids on the expression of PRL-R and (3) to compare the distribution of both the extracellular (EC) and ligand binding (LB) domains of the PRL-R on the hypothalamic dopaminergic neurons by applying double label immunocytochemistry for the different domains of PRL-R and for tyrosine hydroxylase (TH). Five- to six-month-old female rats were ovariectomized (OVX) and implanted with either 17 beta-estradiol (E2), progesterone (P4) or received an E2 and a P4 implant (E2 + P4) at the same time. In the periventricular nucleus and in the dorsomedial portion of the middle arcuate nucleus, a dramatic increase in PRL-REC immunoreactivity was observed in E2 implanted rats. This increase was attenuated in E2 + P4 rats, but P4 treatment alone had no effect. Changes in PRL-REC expression were paralleled by changes in serum PRL levels. Interestingly, PRL-REC expression in the rostral arcuate nucleus decreased in P4 implanted rats, however, P4 did not attenuate the E2-induced increase in PRL-REC density. PRL-REC immunostaining was observed on the membrane, in the cytoplasm and in the nucleus. PRL-RLB immunoreactivity was also detectable in the TH positive neurons, but no nuclear staining was observed with this antibody. However, we found a strong PRL-RLB immunostaining in the ependymal lining of the 3rd ventricle and in the processes of tanycytes projecting to the median eminence. These data indicate that (1) all neuroendocrine DAergic cells can be targets for PRL, (2) expression of PRL-R is differentially affected by ovarian steroids in the different TH cell populations, (3) PRL-RLB domain may be involved in trafficking PRL in the median eminence.

Effect of hormones on expression of prolactin receptor messenger ribonucleic acids in pancreatic islets of adult female mice in vitro

We studied the effects of hormones on expression of prolactin receptor (PRL-R) mRNA in pancreatic islets of adult female mice in vitro. We quantified mRNA expression in small amounts of the islet tissue by competitive PCR and one-sided competitive PCR. Fifty pancreatic islets from adult female mice were cultured in a wall for 4 days with or without ovine prolactin (PRL), bovine growth hormone or estradiol-17 beta. PRL (1 microgram/ml) significantly increased the insulin secretion and the amount of PRL-R mRNA relative to that of beta-actin mRNA. Growth hormone (1 microgram/ml) also increased the relative amount of PRL-R mRNA, although it did not significantly increase the insulin secretion. Neither insulin secretion nor the relative amount of PRL-R mRNA was affected by estradiol (100 ng/ml). The ratio of the short form to the long form of PRL-R mRNA was not altered by these hormones. The present observation that PRL increased PRL-R mRNA expression in pancreatic islets thus suggests the possibility that PRL up-regulates the tissue sensitivity to PRL itself during lactation.

Increased expression of prolactin receptor mRNA in adenomyotic uterus in mice

To investigate changes in uterine prolactin receptor (PRLR) expression in advanced uterine adenomyosis induced by ectopic pituitary isograft, the amount of PRLR mRNA was measured, by a quantitative competitive PCR, in both normal uteri and uteri with adenomyosis in mice at 20 days or 4, 5 and 6 months after pituitary grafting. There was no difference in the amount of PRLR mRNA between the normal uteri and uteri with pituitary grafts, at 20 days after grafting. At 4-6 months after the operation, however, uteri with adenomyosis contained 2-10 times more PRLR mRNA than did in intact uteri, and the increased amount accompanied the advance of the pathological disorder. The ratio of the short to the long form of PRLR mRNA was little affected by the progress of adenomyosis. These findings suggest that increases in the amount of functional PRLR are in fact a result of the progress of adenomyotic changes, rather than simply a result of elevated circulating prolactin levels.