Two forms of gonadotropin-releasing hormone (GnRH), GnRH-I and GnRH-II, are commonly present in mammals. The main hormone controlling reproduction is GnRH-I acting through its receptor (GnRHR-I), whereas the function of GnRH-II is unknown. In primates, it has been suggested that GnRH-II is a specific agonist for the structurally distinct GnRHR-II. Here we compared effects of GnRH-I and GnRH-II on intracellular calcium and gonadotropin hormone release in neonatal rat gonadotrophs in vitro and the dependence of agonist actions on cyclic nucleotide levels. Both agonists elevated intracellular calcium and stimulated gonadotropin secretion in a concentration-dependent manner, with comparable peak amplitudes, but GnRH-I was three times more potent than GnRH-II. Antide, a specific GnRHRI antagonist, completely blocked the action of both agonists on gonadotropin release. Inhibition of adenylyl cyclase activity by melatonin and MDL significantly attenuated GnRH-I- and GnRHII- induced calcium signaling and gonadotropin release, whereas inhibition of soluble guanylyl cyclase activity was ineffective. GnRH-II also generated calcium oscillations in a fraction of gonadotrophs not expressing melatonin receptors. These results indicate that GnRH-I and GnRH-II act on the same GnRHR to stimulate gonadotropin release through intracellular calcium and cyclic nucleotide signaling, and that GnRH-II is less potent agonist for this receptor in neonatal rat gonadotrophs.
- MeSH
- adenylátcyklasy metabolismus MeSH
- gonadotropní buňky metabolismus sekrece MeSH
- hormon uvolňující gonadotropiny metabolismus MeSH
- inhibitory adenylylcyklasy MeSH
- krysa rodu rattus MeSH
- luteinizační hormon sekrece MeSH
- novorozená zvířata MeSH
- potkani Wistar MeSH
- protein - isoformy metabolismus MeSH
- vápníková signalizace MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- srovnávací studie MeSH
Activity of some enzymes of a Pb-adapted strain of Rhizopus arrhizus augmented significantly during bioaccumulation of Pb from a chemically defined medium. The mycelium of a Pb-adapted strain exposed to 1 microg/mL Pb in a defined medium for 10 d at 28 +/- 2 degrees C exhibited, relative to a wild-type strain, increased activities of antioxidant enzymes, i.e. SOD, CAT and GPX and of enzymes like AP and PPO involved in defense against pathogens. Another response is a significant increase in the cellular thiol content after 4 d. The responses to Pb exposure thus include an increase in the antioxidant and anti-pathogen defense, and an increased metal-chelating ability.
- MeSH
- antifungální látky metabolismus MeSH
- enzymy metabolismus MeSH
- fungální léková rezistence MeSH
- fungální proteiny metabolismus MeSH
- kultivační média chemie MeSH
- mycelium enzymologie metabolismus účinky léků MeSH
- olovo metabolismus MeSH
- Rhizopus enzymologie metabolismus účinky léků MeSH
- sulfhydrylové sloučeniny metabolismus MeSH
