Axonal transport and subcellular distribution of dopamine-beta-hydroxylase in the cod, Gadus morhua

The adrenergic stress response in fish: control of catecholamine storage and release

In fish, the catecholamine hormones adrenaline and noradrenaline are released into the circulation, from chromaffin cells, during numerous 'stressful' situations. The physiological and biochemical actions of these hormones (the efferent adrenergic response) have been the focus of numerous investigations over the past several decades. However, until recently, few studies have examined aspects involved in controlling/modulating catecholamine storage and release in fish. This review provides a detailed account of the afferent limb of the adrenergic response in fish, from the biosynthesis of catecholamines to the exocytotic release of these hormones from the chromaffin cells. The emphasis is on three particular topics: (1) catecholamine biosynthesis and storage within the chromaffin cells including the different types of chromaffin cells and their varying arrangement amongst species; (2) situations eliciting the secretion of catecholamines (e.g. hypoxia, hypercapnia, chasing); (3) cholinergic and non-cholinergic (i.e. serotonin, adrenocorticotropic hormone, angiotensin, adenosine) control of catecholamine secretion. As such, this review will demonstrate that the control of catecholamine storage and release in fish chromaffin cells is a complex processes involving regulation via numerous hormones, neurotransmitters and second messenger systems.

Influence of sex steroids on the catecholamine biosynthesis in chromaffin tissue from rainbow trout, Salmo gairdneri

The in vitro activities of dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyl transferase (PNMT) were determined in the chromaffin tissue (head kidney) of sex steroid-treated rainbow trout, Salmo gairdneri. In addition, the DBH and PNMT activities were measured in fish at different sexual states. Steroid treatment increased the wet weight of the head kidney, while both DBH and PNMT activities decreased. Although no sex difference in the enzyme activities was detected, a possible correlation between DBH and PNMT activities and increased GSI values was indicated. The presented data suggest that changes in sex steroids during development may affect the catecholamine synthesis in the chromaffin tissue in S. gairdneri.

Storage and release of catecholamines by nervous endings in the isolated heart of the eel (Anguilla anguilla L.)

Experiments performed on isolated perfused hearts of the eel (Anguilla anguilla L.) showed that the heart spontaneously released catecholamines (i.e. Adrenaline, Noradrenaline, Dopamine) suggesting that they take part in the cardiac regulation. Stimulation of cardiac vagus branches significantly increased catecholamines levels, measured in a perfusion medium and simultaneously the heart rate and the systolic pressure. The effect of Desmethylimipramine showed that the catecholamines were released from nervous endings and not from endothelial cells.

Activity of tyrosine hydroxylase (EC 1.14.16.2) from chromaffin and nervous tissue of the Atlantic cod, Gadus morhua

1. The activity of tyrosine hydroxylase (TH; EC 1.14.16.2) was estimated in vitro in crude tissue homogenates from the posterior cardinal veins (chromaffin tissue) and the coeliac ganglion (adrenergic neurons) of the Atlantic cod, Gadus morhua. 2. TH from the chromaffin tissue showed its highest activity at pH = 6.0 and a temperature of 30-35 degrees C, and was stimulated by low concentrations of catalase (20 micrograms/ml). 3. Estimations of the absolute TH activity in vitro showed values of 110 +/- 30 nmol/g X hr for the chromaffin tissue and 1120 +/- 280 nmol/g X hr for the coeliac ganglion.

Dopamine-beta-hydroxylase activity in the axillary bodies, the heart and the splanchnic nerve in two elasmobranchs, Squalus acanthias and Etmopterus spinax

1. The activity of dopamine-beta-hydroxylase (DBH) was examined in tissues from Squalus acanthias and Etmopterus spinax using tyramine as substrate. 2. The activity of DBH in axillary bodies in Squalus was 19040 +/- 240 nmol/g per hr and in Etmopterus 6120 +/- 245 nmol/g per hr. 3. DBH activity in nervous tissue, i.e. the splanchnic nerve (together with coeliac artery) was found to be 123 +/- 41 nmol/g per hr in Squalus and 384 +/- 62 nmol/g per hr in Etmopterus. 4. In Squalus heart DBH activity was undetectable, while Etmopterus heart had DBH activity both in atrium and ventricle, 40 +/- 13 and 18 +/- 8 nmol/g per hr respectively. 5. A small amount of DBH activity was found in Squalus blood plasma, 2 +/- 0.7 nmol/ml per hr. 6. The DBH activity gave high formation of octopamine in a wide temperature range from 24.5 to 32 degrees C.

Activity of dopamine-beta-hydroxylase (DBH) and phenylethanolamine-N-methyl transferase (PNMT) in heart, lung and chromaffin tissue from the Florida spotted gar Lepisosteus platyrhincus (Holostei)

The activities of dopamine-beta-hydroxylase (DBH; E.C. 1.14.17.1) and phenylethanolamine-N-methyl transferase (PNMT; E.C. 2.1.1.10) were estimated in homogenates from the heart, the lung and the posterior cardinal veins from Lepisosteus platyrhincus. Both enzymes could be detected in all three tissues, the activity being highest in the chromaffin tissue of the posterior cardinal veins. The activity of DBH estimated in the present in vitro experiments was about 100-fold higher than the PNMT activity. Preliminary experiments with substrate specificity for the PNMT shows a low (heart) or undetectable (lung and cardinal veins) methylation of phenylethylamine, and the specific PNMT inhibitor SK&F 64139 (1 micro M) lowered the PNMT activity in all three tissues by 55-75%. The presence of PNMT in the adrenergically innervated tissues puts Lepisosteus with the teleosts and the amphibians among vertebrates with capacity for truly adrenergic, as opposed to noradrenergic, transmission.