Evidence for multiple prolactin receptor transcripts in the turkey

Multiple prolactin receptor (PRL-R) mRNA transcript isoforms have been identified in mammals, but there are conflicting reports concerning the number of avian PRL-R isoforms. We hypothesized that multiple turkey PRL-R transcript isoforms exist and that PRL-R mRNA abundance may be related to reproductive status. Two turkey PRL-R cDNA fragments were generated using reverse transcriptase polymerase chain reaction (RT-PCR) that displayed a high degree of similarity to mammalian and avian PRL-R. Northern blot analysis of poly A⁺ mRNA hybridized to a turkey PRL-R riboprobe revealed a 3.1-kb band in the liver, oviduct, and testes. Additional 1.5- and 10.7-kb transcripts were found in the liver and testes, respectively. Hybridization of the same Northern blot to a chicken PRL-R probe verified the presence of a 3.1-kb transcript in all three tissues. A Northern blot was used to examine turkey PRL-R transcript isoform expression in laying hens. A 3.1-kb band was found in the pineal, infundibulum, magnum, isthmus, kidney, and intestine. In addition, 10.7- and 7.3-kb bands were detected in the pineal, magnum, isthmus, and intestine. Turkey PRL-R transcript isoforms were also examined throughout the reproductive cycle. The 10.7-, 7.3-, and 3.1-kb isoforms were detected in the oviduct, intestine, and pineal during each reproductive state. Turkey PRL-R mRNA levels were also compared during the reproductive cycle. Turkey PRL-R mRNA levels were greatest in laying hen pineal glands (P < 0.05) and in incubating hen oviducts. This study provides the first evidence for multiple PRL-R mRNA transcript isoforms in turkeys.