Expression of the messenger ribonucleic acids for insulin-like growth Factor-I and insulin-like growth factor binding proteins in porcine corpora lutea

• Published in: Biology of reproduction 1996-02, Vol.54 (2), p.339-346
• Main Authors: GADSBY, J. E, LOVDAL, J. A, SAMARAS, S, BARBER, J. S, HAMMOND, J. M
• Format: Article
• Language: English
• Subjects: Animals; arn mensajero; arn messager; binding proteins; Biological and medical sciences; Blotting, Northern; cells; cellule; celulas; cerdas; cerdo; ciclo estral; corps jaune; corpus luteum; Corpus Luteum - metabolism; cuerpo luteo; cycle oestral; expresion genica; expression des genes; facteur de croissance igf; factor de crecimiento igf; Female; Fundamental and applied biological sciences. Psychology; Gene Expression; Hormone metabolism and regulation; insulin like growth factor; Insulin-Like Growth Factor Binding Protein 2 - genetics; Insulin-Like Growth Factor Binding Protein 3 - genetics; Insulin-Like Growth Factor Binding Protein 4 - genetics; Insulin-Like Growth Factor Binding Protein 5 - genetics; Insulin-Like Growth Factor Binding Protein 6 - genetics; Insulin-Like Growth Factor Binding Proteins - genetics; Insulin-Like Growth Factor I - genetics; Mammalian female genital system; messenger rna; oestrous cycle; porcin; proteinas aglutinantes; proteine de liaison; RNA, Messenger - metabolism; sows; Swine; truie; Vertebrates: reproduction
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod54.2.339

In the pig, the corpus luteum (CL) can develop and function autonomous of pituitary gonadotropins for approximately 12 days. We hypothesized that the insulin-like growth factor (IGF) system may play an autocrine/paracrine luteotrophic role(s) during this period. In this study, we monitored the expression (i.e., steady-state levels of mRNAs) of IGF-I and IGF binding proteins (IGFBP)-2, -3, -4, -5, and -6 mRNAs in whole CL and in small and large luteal cells on Days 4-16 of the estrous cycle. CL were dissociated with collagenase, and large and small luteal cells were isolated by centrifugal elutriation. Whole CL and luteal cells were extracted to isolate total or poly(A)+ RNA, which was subjected to Northern and/or dot-blot analyses using [32P]-labeled cDNA probes for IGF-I and IGFBP-2, -3, -4, -5, and -6. Northern blots showed readily detectable transcripts for IGF-I (6.7 and 0.9 kb), IGFBP-2 (1.8 kb), IGFBP-3 (2.8 kb), IGFBP-4 (2.6 kb), and IGFBP-5 (6.0 kb), but not for IGFBP-6. IGFBP-3 and -5 transcripts were observed mainly in small luteal cells, while IGFBP-2 and -4 were seen in both cell types. Dot-blot analyses for IGF-I and IGFBP-3 mRNAs were performed on total RNA from small and large luteal cells; blots were counter-probed with 3-phosphoglyceraldehyde dehydrogenase (p-GAD) cDNA to assess RNA quantity and quality. IGF-I mRNA (ratio IGF-I:p-GAD mRNA) expression was approximately 2-fold greater in small than in large luteal cells on Days 4-10. However, steady-state levels of IGF-I mRNA in small, but not large, luteal cells decreased significantly on Days 12-16 (vs. Days 4-10). IGFBP-3 mRNA expression was significantly greater (approximately 3-fold) in small than in large luteal cells but did not vary significantly between Days 4-10 and 12-16 for either cell type. We conclude that porcine CL express mRNAs for IGF-I and IGFBP-2, -3, -4, and -5.