Effects of environmental osmolality on release of prolactin, growth hormone and ACTH from the tilapia pituitary
| Autor: | Andre P. Seale, Tetsuya Hirano, Shingo Kajimura, E.G. Grau, Larry G. Riley, Robert M. Dores, Thomas A. Leedom |
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| Rok vydání: | 2002 |
| Předmět: |
Male
medicine.medical_specialty Oreochromis mossambicus food.ingredient Acclimatization Hypertonic Solutions Fresh Water Environment Endocrinology food Adrenocorticotropic Hormone Internal medicine medicine Extracellular Animals Seawater biology Osmotic concentration Osmolar Concentration Tilapia Euryhaline biology.organism_classification Prolactin Plasma osmolality Hypotonic Solutions Growth Hormone Pituitary Gland Osmoregulation Female Animal Science and Zoology |
| Zdroj: | General and Comparative Endocrinology. 128:91-101 |
| ISSN: | 0016-6480 |
| Popis: | Prolactin (PRL) plays a central role in freshwater (FW) adaptation in teleost fish. Evidence now suggests that growth hormone (GH) acts in the seawater (SW) adaptation in at least some euryhaline fish. Reflecting its important role in FW adaptation, plasma levels of PRL188 and PRL177 are higher in tilapia (Oreochromis mossambicus) adapted to FW than in those adapted to SW. A transient but significant increase in plasma GH was observed 6 h after transfer from FW to SW. Elevated plasma PRL levels were seen in association with reductions in plasma osmolality after blood withdrawal in FW fish whereas no significant change was seen in plasma GH levels. When pituitaries from FW tilapia were incubated for 7 days, secretion of both PRLs was significantly greater in hyposmotic medium than in hyperosmotic medium for the first 24 h. Secretion of GH from the same pituitary was relatively low during this period compared with PRL secretion. No consistent effect of medium osmolality on GH release was seen for the first day, but its cumulative release was increased significantly in hyperosmotic medium after 2 days and thereafter. On the other hand, ACTH release was extremely low compared with the secretion of PRLs and GH and there was no consistent effect of medium osmolality. These results indicate that PRL release from the tilapia pituitary is stimulated both in vivo and in vitro as extracellular osmolality is reduced, whereas the secretion of GH increases temporarily when osmolality is increased. ACTH seems to be relatively insensitive to the changes in environmental osmolality. |
| Databáze: | OpenAIRE |
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