Neurohypophysial hormone functions in marsupials

Bathgate, Ross A. D. (1994). Neurohypophysial hormone functions in marsupials PhD Thesis, School of Biomedical Sciences, University of Queensland. doi:10.14264/uql.2016.429

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Author Bathgate, Ross A. D.
Thesis Title Neurohypophysial hormone functions in marsupials
School, Centre or Institute School of Biomedical Sciences
Institution University of Queensland
DOI 10.14264/uql.2016.429
Publication date 1994-01-01
Thesis type PhD Thesis
Supervisor Conrad Semia
Total pages 170
Language eng
Subjects 06 Biological Sciences
Formatted abstract
Eutherian mammals secrete the nonapeptides oxytocin (OT) and arginine vasopressin (AVP) as their neurohypophysial hormones. OT has well documented roles in lactation and parturition whereas AVP is involved in fluid homeostasis and blood pressure regulation. However the functions of these peptides are much wider than these and include roles during various types of stress. Marsupials secrete a variety of neurohypophysial hormones in addition to or instead of OT and AVP. There is very little known about the roles of these different OT- and AVP-like peptides in marsupials. This thesis has primarily involved characterization and localization of these peptides leading to some preliminary investigations into the possible functions of these peptides in marsupials. The brushtail possum (Trichosurus vulpecula) has been used as the primary model with some studies also on the northern brown bandicoot (Isoodon macrourus). The brushtail possum secretes the typically reptilian mesotocin (MT) together with AVP as its neurohypophysial hormones, whereas the bandicoot secretes OT and MT together with AVP and lysine- vasopressin (LVP). The brain distribution and plasma release of both MT and OT were studied in the bandicoot and the brain distribution and plasma release of AVP was studied in the possum. The regulation of the plasma release of MT and AVP by various factors including different types of stress was also studied in the possum. Neurohypophysial hormones are also found in a number of peripheral tissues in eutherian mammals and other vertebrates. There is also some evidence for tissue specific expression of neurohypophysial hormones. Therefore peripheral tissues of the possum and bandicoot were examined for the presence of neurohypophysial hormones. As the functions of peptides are mediated via receptors this thesis has also examined OT and AVP receptors in the possum, OT and AVP receptors In the possum were compared to OT and AVP receptors in the rat. As OT receptors have not previously been characterized in the testis of eutherian mammals the rat testis OT receptor was characterized together with the testis AVP receptor for comparison to OT and AVP receptors in the possum testis. 

MT and OT were measured In the brain and plasma of the northern brown bandicoot (Isoodon macrourus) using reverse-phase high-performance liquid chromatography (HPLC) and specific radloimmunoassays (RIA) for both OT and MT. Both peptides were found in the pituitary (1.25 ± 0.10 µg/MT; 0.725 ± 0.077 µg/OT) and hypothalamus (38.37 ± 6.46 ng/MT; 19.1 ± 4.61 ng/OT) (mean ± SEM). Concentrations in the cerebral cortex were very low and consequently only two animals had detectable levels (311 and 154 pg/MT; 360 and 92 ng/OT). Basal plasma concentrations ranged from 1.5 - 8.1 pg/ml for both peptides (n=14) and were elevated by the combined stress of surgery, anaesthesia and hypovolemia.   .....................................................
Keyword Neurohypophysis
Marsupials -- Reproduction -- Endocrine aspects

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
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