Changes in the pituitary content of prolactin (PRL) and in the ratio of immunoreactive forms of PRL were measured during a reproductive cycle in turkey hens. Low levels of PRL were observed in pituitary glands from sexually immature, out-of-lay and moulting hens. Higher levels were present during the egg laying period and the highest levels were detected in hens expressing incubating behaviour. Two immunoreactive bands of apparent molecular weights of 24 and 27 kDa were visualised on western blots, corresponding to the non-glycosylated (NG-) and glycosylated (G-) forms of PRL, respectively. The percentage of G-PRL was about 60 in sexually immature and egg laying hens. In pituitaries from incubating, out-of-lay and moulting hens the percentage of G-PRL was about 70, 38 and 33, respectively. Thus, higher percentages of G-isoforms (27 kDa) were associated with high levels of total PRL and Iower percentages were associated with low levels of PRL content in the pituitary gland. Digestion of the isoforms with N-glycosidase F resulted in a single band with an apparent molecular weight of 24 kDa. Partial deglycosylation was achieved using neuraminidase, whereas digestion with O-glycosidase had no apparent effect on the isoforms. Thus, G-PRL has N-linked carbohydrates containing sialic acid. In order to study the in vitro release of the PRL isoforms, pituitary glands from turkeys at various physiological stages were stimulated by cVIP in a perifusion system. Total PRL content and the ratio of immunoreactive PRL isoforms in the perifusate were monitored. All the perifused pituitaries responded to cVIP stimulation by increasing the release of PRL. Two immunoreactive bands corresponding to the ones detected in pituitary extracts were detected by western blotting. The G-PRL (27 kDa) was predominant in samples from egg laying and incubating hens and the NG-PRL (24 kDa) was predominant in samples from out-of-lay and moulting hens. No change in the ratio of isoforms released was / A competitive reverse transcription polymerase chain reaction assay was developed in order to semi-quantify the PRL mRNA in individual pituitary glands from turkey embryos and poults. Pituitary content and plasma levels of PRL were also monitored, and the PRL isoforms present in the pituitary gland were detected. The levels of PRL mRNA remained low until five days before hatching, increased until the day of hatch, plateaued during the first three days of age and significantly increased at two weeks of age. Similar changes were observed in pituitary content and plasma concentrations of PRL which were highly correlated. Two immunoreactive bands corresponding to the NG- and G-PRL detected in adult pituitary gland were visualised on western blots. The percentage of G-PRL in pituitary glands were 31.5, 48.6, 48.0 and 56.2 at 22 and 27 days of incubation and at I and 7 days of age, respectively. Thus, higher percentages of G-PRL (27 kDa) were associated with higher levels of total PRL in the pituitary gland.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35854 |
| Date | January 1999 |
| Creators | Bédécarrats, Grégoy. |
| Contributors | Zadworny, David (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Animal Science.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001659363, proquestno: NQ50110, Theses scanned by UMI/ProQuest. |
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