Mesotocin and arginine-vasopressin in the corpus luteum of an Australian marsupial, the brushtail possum (Trichosurus vulpecula).
The neuropeptide hormones arginine-vasopressin (AVP) and oxytocin (OT) have been found in the ovarian follicles and corpora lutea (CL) of many eutherian mammals. In ruminants, there is persuasive evidence that luteal OT is involved in luteolysis via stimulation of uterine prostaglandins. However, based on scant evidence, the marsupial ovary has been viewed as being devoid of OT-like and AVP-like peptides. In this study, corpora lutea from the brushtail possum were examined for OT, AVP, and mesotocin (MT) by a combination of reverse phase HPLC, radioimmunoassay, and immunohistochemistry (IHC). Peptides extracted from each of five CL were separated by HPLC and each fraction was assayed for AVP, MT, and OT. Two immunoreactive peaks were found, corresponding to AVP and MT standards. The amount of each peptide was 8.7 +/- 2.22 pmol MT/g (mean +/- SEM) and 5.7 +/- 1.0 pmol AVP/g, respectively. The mean MT/AVP ratio was 1.55 compared to 0.26 for the pituitary. IHC (streptavidin-peroxidase method) of Bouin's-fixed CL showed staining for MT in the cytoplasm of luteal cells which was absent in stromal tissue and nonluteal ovarian tissue. Not all luteal cells were immunopositive and no topographical distribution of stained cells was observed. IHC localization of AVP was not attempted. It was concluded that the CL of the brushtail possum contains low quantities of MT and AVP, which in the case of MT is probably synthesized by the immunochemically staining cells of the CL.
Sernia
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C
Department of Physiology and Pharmacology, University of Queensland, Australia.
Bathgate
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RA
Gemmell
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RT
D000818:Animals; D001127:Arginine Vasopressin / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D003338:Corpus Luteum / Q000737:chemistry*; D005260:Female; D007150:Immunohistochemistry; D009893:Opossums / Q000378:metabolism*; D010121:Oxytocin / Q000031:analogs & derivatives* / Q000032:analysis
D001127:Arginine Vasopressin; C001713:mesotocin; D010121:Oxytocin