No description available.

Changes in the levels of expression of the prolactin receptor (PRLR) mRNA in the pituitary gland, hypothalamus, liver, pancreas, kidney and gonad from embryonic day (ED) 15 and ED21 to 1 day post-hatch, respectively, in chickens and turkeys were measured by real-time PCR. In both species, PRLR mRNA increased from low levels during the last week of ED to reach maxima at the peri-hatch period. Similarly, circulating levels of prolactin (PRL) also increased during this interval and were correlated with the observed increases in tissue content of PRLR mRNA. This suggested that PRL was up-regulating its own receptor during late embryogenesis. In support of this, in vitro stimulation of the pituitary gland of turkeys with VIP on ED24 resulted in a 4 fold and 3 fold increase in PRL and PRLR, respectively. Stimulation with VIP of either the hypothalamus or gonad had no effect on either levels of the PRLR transcript. This suggests that VIP acts indirectly through increased PRL to upregulate the number of receptors. In order to investigate the transcription of genes that may be induced/suppressed by PRL, suppressive subtractive hybridization (SSH) libraries from control or VIP stimulated ED24 turkey pituitary glands were constructed. Stimulation with VIP resulted in a 5.7 and 2.8 fold increase in media and pituitary content of PRL, respectively. The changes in PRL were consistent with endogenous levels of PRL observed just prior to hatch. Following sequence analysis of random clones (n=96) from each library, a total of 145 non-redundant putative genes were obtained. About 51% of the putative genes have as yet no assigned function, whereas, 15% were housekeeping genes and 34% had known functions within various pathways. Real-time PCR was used to confirm the differential expression of 21 of these genes in VIP treated and control pituitaries. Since the majority of these genes were expressed at levels consistent with the direction of subtraction, these data suggest that these libraries may be useful to study the direct and indirect effects of increasing levels of PRL on anterior pituitary function at about the time of hatch.