Regulation of Lh and Gh Release by Isotocin in a Teleost, the Ricefield Eel Monopterus albus
Wei Yang, Ning Zhang, Yangsheng Wu, Dong Chen, Lihong Zhang, Weimin Zhang*
Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, P.R. China
The neurohypophyseal hormone oxytocin (Oxt) has been shown to regulate the synthesis and release of adenohypophyseal hormones in rats. However, little is known about the functional roles of Oxt-like neuropeptides in the adenohypophysis of nonmammalian vertebrates. In the present study, cDNAs encoding ricefield eel isotocin (Ist) receptor 1 (Istr1) and 2 (Istr2), oxytocin-like receptors, were isolated and specific antisera were generated, respectively. RT-PCR and Western blot analysis detected the presence of both Istr1 and Istr2 in the brain and pituitary but differential expression in peripheral tissues including liver and kidney, where only Istr1 was detected. In the pituitary, immunoreactive Istr1 and Istr2 were differentially distributed, with the former mainly in adenohypophyseal cell layers adjacent to the neurohypophysis whereas the latter in peripheral areas of the adenohypophysis. Double immunofluorescent images showed that immunostaining of Istr1 was localized to growth hormone (Gh) cells, and immunostaining of Istr2 was localized to Lh cells. Neither of them was expressed in Prl or Fsh cells.
Ist inhibited Gh release in primary pituitary cells of ricefield eels and increased Gh contents in the pituitary gland of ricefield eels at 6 hrs after in vivo administration. Ist inhibition of Gh release is probably mediated by cAMP, PKC/DAG, and IP3/Ca2+ pathways. In contrast, Ist stimulated Lh release in primary pituitary cells of ricefield eels and decreased Lh contents in the pituitary gland of ricefield eels at 2 hrs after in vivo administration. Ist induction of Lh release is probably mediated by IP3/Ca2+ pathways. Results of the present study demonstrated that Ist may inhibit Gh release in ricefield eels via Istr1 while stimulate Lh release via Istr2, which provides evidence for the direct regulation of adenohypophyseal hormones by the Oxt-like neuropeptide in the pituitary of non-mammalian vertebrates.
Acknowledgements: Supported by NSFC to WZ (31672638 and 31372513) and LZ (31572604).
Key Words: Monopterus albus, isotocin, isotocin receptor, Gh, Lh
Wei Yang, Ning Zhang, Yangsheng Wu, Dong Chen, Lihong Zhang, Weimin Zhang*
Institute of Aquatic Economic Animals and Guangdong Province Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, P.R. China
The neurohypophyseal hormone oxytocin (Oxt) has been shown to regulate the synthesis and release of adenohypophyseal hormones in rats. However, little is known about the functional roles of Oxt-like neuropeptides in the adenohypophysis of nonmammalian vertebrates. In the present study, cDNAs encoding ricefield eel isotocin (Ist) receptor 1 (Istr1) and 2 (Istr2), oxytocin-like receptors, were isolated and specific antisera were generated, respectively. RT-PCR and Western blot analysis detected the presence of both Istr1 and Istr2 in the brain and pituitary but differential expression in peripheral tissues including liver and kidney, where only Istr1 was detected. In the pituitary, immunoreactive Istr1 and Istr2 were differentially distributed, with the former mainly in adenohypophyseal cell layers adjacent to the neurohypophysis whereas the latter in peripheral areas of the adenohypophysis. Double immunofluorescent images showed that immunostaining of Istr1 was localized to growth hormone (Gh) cells, and immunostaining of Istr2 was localized to Lh cells. Neither of them was expressed in Prl or Fsh cells.
Ist inhibited Gh release in primary pituitary cells of ricefield eels and increased Gh contents in the pituitary gland of ricefield eels at 6 hrs after in vivo administration. Ist inhibition of Gh release is probably mediated by cAMP, PKC/DAG, and IP3/Ca2+ pathways. In contrast, Ist stimulated Lh release in primary pituitary cells of ricefield eels and decreased Lh contents in the pituitary gland of ricefield eels at 2 hrs after in vivo administration. Ist induction of Lh release is probably mediated by IP3/Ca2+ pathways. Results of the present study demonstrated that Ist may inhibit Gh release in ricefield eels via Istr1 while stimulate Lh release via Istr2, which provides evidence for the direct regulation of adenohypophyseal hormones by the Oxt-like neuropeptide in the pituitary of non-mammalian vertebrates.
Acknowledgements: Supported by NSFC to WZ (31672638 and 31372513) and LZ (31572604).
Key Words: Monopterus albus, isotocin, isotocin receptor, Gh, Lh