Modulation of catecholamine storage and release by the pituitary-interrenal axis in the rainbow trout, Oncorhynchus mykiss

Abstract

This study examined the effects of pituitary-interrenal hormones on catecholamine storage and release in the rainbow trout Oncorhynchus mykiss. An extract of trout pituitary elicited the release of adrenaline, but not noradrenaline, using an in situ perfusion preparation. A variety of doses of adrenocorticotropic hormone (2-2000 mU) caused the release of both catecholamines in situ which was unaffected by pre-treatment with the ganglion blocker, hexamethonium, or the serotonergic receptor antagonist, methysergide, but was abolished in calcium-free media. Intra-arterial injections of adrenocorticotrophic hormone in vivo caused an elevation of plasma adrenaline but not noradrenaline levels. Injections of cortisol in situ did not elicit catecholamine release. Trout given an intraperitoneal implant of cortisol (50 mg.kg-1 body weight) had significantly higher plasma cortisol concentrations when compared to controls after 7 days of implantation. Increases in the levels of stored catecholamines were observed in various regions of the kidney and posterior cardinal vein following 3 and 7 days of cortisol treatment. The ability of the chromaffin cells to release catecholamines in response to cholinergic stimulation was assessed in situ after 7 days of treatment. Basal (non-stimulated) adrenaline outflowing perfusate levels were greater in the cortisol-treated fish. Cortisol treatment increased the responsiveness of the catecholamine release process to low doses of the cholinoceptor agonist carbachol. Three or 7 days of cortisol treatment did not alter the in vitro activity of the enzyme phenylethanolamine-N-methyl transferase. The results of this study demonstrate that interactions within the pituitary-adrenal axis can influence both catecholamine storage and release in the rainbow trout.

Bigger is not better: cortisol-induced cardiac growth and dysfunction in salmonids

“…The increased f H could reflect increased catecholaminergic innervation or decreased cholinergic tone on the heart. Reid et al (1996) showed that cortisol administration in rainbow trout altered the secretion of catecholamines, which are well known for their inotropic effects on the heart. By pharmacologically blocking both adrenergic and cholinergic receptors, we found that the increased f H in cortisol-treated fish was probably due to a reduction in cholinergic tone rather than an increase in adrenergic signalling.…”

Are hsps suitable for indicating stressed states in fish?

“…Cortisol is released from the interrenal tissue, located in the head kidney, in response to several pituitary hormones but most potently to the adrenocorticotrophic hormone (ACTH; see Balm et al, 1994). ACTH may also stimulate the release of the CAT epinephrine, and chronically increased levels of cortisol may affect CAT storage and release in trout (Reid et al, 1996). As both the chromaffin and the interrenal tissues in fish lie in close proximity, a paracrine effect for these stress hormones may exist (Reid et al, 1996).…”

“…ACTH may also stimulate the release of the CAT epinephrine, and chronically increased levels of cortisol may affect CAT storage and release in trout (Reid et al, 1996). As both the chromaffin and the interrenal tissues in fish lie in close proximity, a paracrine effect for these stress hormones may exist (Reid et al, 1996). The physiological actions of both hormones are dependent on appropriate receptors on target tissues.…”

Hematological Importance of Pseudoeosinophilic Granulocytes in Acclimation of Common Carp (Cyprinus Carpio Linnaeus, 1758)

“…In the case of monocytes, complex fish proinflammatory cytokines triggered mobilization (27,28) and they cross from pronephros melanomacrophage centers to peripheral circulation (29). Decreased Ly count was probably result of the fact that these cells are involved in the cellular and humoral immune response and could not easily leave the anterior part of pronephros in which they were mainly localized, Total WBC of experimental males was very similar to WBC of control males, but the proportion of different leukocyte types was changed.…”