RESUMEN
The effect of hormone treatment on the abundance of Na+-K+-ATPase alpha- and beta-subunit mRNA in Sparus sarba branchial tissue was investigated. Groups of seawater (33/1000) and hypo-osmotic (6/1000) acclimated fish were injected daily, with either saline, cortisol, recombinant bream growth hormone (rbGH) or ovine prolactin (oPRL). Total RNA from branchial tissue was analyzed by Northern blotting using PCR amplified Na+-K+-ATPase alpha- and beta-subunit cDNA clones. Na+-K+-ATPase alpha- and beta- subunit transcripts of 3.3kb and 2.4kb respectively, were detected and their abundance, after hormone treatment was assessed using RNA dot blots. The abundance of subunit mRNAs increased 1.4-1.9 fold, relative to controls, after cortisol treatment. The alpha:beta mRNA ratio also increased in cortisol treated seawater acclimated fish. Growth hormone treatment did not cause any significant changes in Na+-K+-ATPase subunit mRNA, whereas prolactin significantly reduced alpha-subunit mRNA levels by approximately 0.5 fold in both seawater and hypo-osmotic conditions. The data from this study add further support to the generally accepted roles that cortisol and prolactin have in the modulation of Na+-K+-ATPase activity. It can be concluded from this study that S. sarba branchial Na+-K+-ATPase subunit expression is multihormonally regulated.
Asunto(s)
Región Branquial/efectos de los fármacos , Hormona del Crecimiento/farmacología , Hidrocortisona/farmacología , Perciformes , Prolactina/farmacología , ARN Mensajero/metabolismo , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Northern Blotting , Región Branquial/enzimología , Cartilla de ADN/química , ADN Complementario/metabolismo , Isoenzimas , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , ATPasa Intercambiadora de Sodio-Potasio/genéticaRESUMEN
Plasma cortisol, pituitary adrenocorticotropin and arginine vasotocin (AVT) contents, and hypothalamic urotensin I (UI) and AVT contents were determined in urophysectomized goldfish (1 wk) with and without dexamethasone injections. Urophysectomy produced marked increases in plasma cortisol. These marked increases could not be observed in urophysectomized fish that received dexamethasone injections. These findings suggest that the hypothalamo-pituitary-interrenal axis is activated after urophysectomy. This activation may be due to the enhanced secretion of U I from the goldfish hypothalamus, suggesting that U I may be a fish corticotropin-releasing factor.