Abstract
Oxytocin (OT) is a crucial regulator of reproductive behaviors, including parturition in mammals. Arg-vasopressin (AVP) is a nonapeptide homologous to Arg-vasotocin (AVT) in teleosts that has comparable affinity for the OT receptor. In the present study, ovoviviparous guppies (Poecilia reticulata) were used to study the effect of AVT on delivery mediated by the activation of prostaglandin (PG) biosynthesis via isotocin (IT) receptors (ITRs). One copy each of it and avt and two copies of itrs were identified in guppies. The results of the affinity assay showed that various concentrations of AVT and IT (10−6, 10−7, and 10−8 mol/L) significantly activated itr1 (P < 0.05). In vitro experiments revealed significant upregulation (P < 0.05) of cyclooxygenase 2 (cox2), which is the rate-limiting enzyme involved in PG biosynthesis, and itr1 by AVT and IT. Furthermore, dual in situ hybridization detected positive signals for itr1 and cox2 at the same site, implying that ITR1 may regulate cox2 gene expression. Measurement of prostaglandin F2a (PGF2a) concentrations showed that AVT induced PGF2a synthesis (P < 0.05) and that the effect of IT was not significant. Finally, intraperitoneal administration of PGF2a significantly induced premature parturition of guppies. This study is the first to identify and characterize AVT and ITRs in guppies. The findings suggest that AVT promotes PG biosynthesis via ITR and that PGF2a induces delivery behavior in ovoviviparous guppies.
Highlights
Oxytocin (OT) is a highly conserved nonapeptide that was the first peptide hormone with determined molecular structure [1]
The present study investigated the molecular mechanism by which AVT and IT stimulate prostaglandin F2a (PGF2a) synthesis via the isotocin receptor (ITR) and subsequently trigger the initiation of parturition in guppies to determine the role of the interaction of AVT and IT with ITR and PGF2a in the regulation in live bearing guppy
Genomic data mining and gene cloning showed that the open reading frame (ORF) of avt (MW050982) is 456 bp and encodes a 151-amino acid precursor with a predicted signal peptide of 16 aa (Figure 1A)
Summary
Oxytocin (OT) is a highly conserved nonapeptide that was the first peptide hormone with determined molecular structure [1]. OT has various effects and is involved in many physiological processes, especially reproduction. OT has a notable effect on the induction of parturition and smooth muscle contraction and has been used as a medicine in the clinic [2,3,4,5]. Arg-Vasotocin in Ovoviviparous Teleost Reproduction mechanism governing the effect of IT on ovulation in oviparous teleosts has not been determined. Injection of a combination of Ovaprim and IT activated ovulation in Hoven’s carp (Leptobarbus hoevenii) [13]. The functions of IT in the reproduction are limited to the induction of premature parturition in guppy (Poecilia reticulata) [14]. Other studies suggested that AVT may regulate sex-related reproductive behaviors
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