Expression and localization of prolactin receptor messenger ribonucleic acid in red deer ovary during the estrous cycle and pregnancy

In this study, expression of the prolactin receptor (PRL-R) gene in the ovaries of cycling and pregnant red deer (Cervus elaphus) hinds was investigated. A 1.9-kilobase (kb) cDNA encoding the cervine long-form PRL-R was amplified by reverse transcriptase polymerase chain reaction from corpus luteum (CL) and liver poly(A)+ RNA. Northern hybridization revealed a major mRNA transcript of 3.5 kb in both tissues. PRL-R mRNA transcripts were localized by in situ hybridization in 15-mu m frozen sections of red deer ovaries, collected during the estrous cycle and early pregnancy, with homologous 45-mer [S-35]dATP-labeled sense and antisense oligonucleotide probes. Specific hybridization was assessed by measurement of autoradiograph optical density (OD) in CL, follicles, and stroma. PRL-R mRNA expression was higher (p < 0.001) in the CL (OD = 22.2 +/- 3.77, 11 CL) than in follicles (OD = 2.8 +/- 0.10, n = 224 follicles) and was undetectable in the stroma (OD < 1, limit of detection). No differences in abundance of PRL-R mRNA were observed between follicles divided on the basis of size, health vs. atresia, or stage of estrous cycle or pregnancy, or between CL from pregnant and nonpregnant hinds. In the follicles, PRL-R mRNA was localized to the theca layer. These results suggest a direct role for PRL in red deer ovarian physiology during the estrous cycle and pregnancy.