Catecholamines in head and body blood of eels and rats

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.

Interaction of salmon glucagon, glucagon-like peptide, and epinephrine in the stimulation of phosphorylase a activity in fish isolated hepatocytes

The simultaneous addition of epinephrine and salmon glucagon to catfish (Ictalurus melas) and trout (Salmo gairdneri) hepatocytes did not induce greater increases in glycogen phosphorylase a activity and in glucose release than those caused by epinephrine alone. The effects of epinephrine are greater than those of glucagon. Propranolol added to the hormonal pool blocked the epinephrine effects. In trout cells, epinephrine and glucagon-like peptide (GLP) had similar effects and when they were added simultaneously the stimulation of metabolic indices was higher compared to that obtained with either epinephrine or GLP. However, the effects were not additive. In the presence of epinephrine plus GLP the inhibitory effect of propranolol was not evident, due to the effect induced by GLP, on which propranolol was not effective. This may indicate that epinephrine masks the GLP effect. Results could mean that epinephrine and glucagon-family peptides act in catfish and trout hepatocytes through different receptors on the same pathway leading to glycogen phosphorylase a activation.

Catecholamines, opioid peptides, and true opiates in the chromaffin cells of the eel: immunohistochemical evidence

An immunohistological analysis of the chromaffin cell system of the American eel revealed the presence of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) in all cells. However, phenylethanolamine-N-methyltransferase (PNMT) was seen only in a fraction of the chromaffin cells. This suggests the presence of both norepinephrine and epinephrine cells and the absence of specific dopamine cells. The chromaffin cells are most numerous in the anterior region of the posterior cardinal vein, where they occupy a subendothelial position. Their number decreases caudally, and a relatively small number are present in the larger veins of the opisthonephric kidney. No PNMT-positive cells were identified in this region, although a radioenzymatic assay had previously shown the presence of epinephrine. Methionine-enkephalin immunoreactivity seems to be restricted to the chromaffin cells. However, particularly large amounts of leucine immunoreactivity occur in the interrenal cells, with smaller quantities in the chromaffin cells. The chromaffin cells of the eel also contain morphine immunoreactivity.

The sources of plasma catecholamines in the American eel, Anguilla rostrata

The origin of the catecholamines (CAs) in the systemic blood of the American eel, Anguilla rostrata, was studied by three approaches: (1) determination of the CA content of tissues suspected to release large quantities of dopamine, norepinephrine, and/or epinephrine into the circulation; (2) measurement of local CA titers in selected regions of the cardiovascular system; and (3) removal of tissues with high CA concentrations, followed by determination of its impact on stimulated CA release. Large quantities of all three CAs were found in the walls of the posterior cardinal veins, from their caudal origin within the opisthonephric kidney to their termination in the ductus Cuvieri. Near the ductus Cuvieri, the CA concentration was 1-3 orders of magnitude above that in other tissues. In this region, which contains the presumed adrenal medulla equivalent, occur the highest plasma levels of the CAs. Strong CA release also in the opisthonephric kidney region raises the question if these CAs affect locally the kidney functions, and/or via the hepatic portal vein (which originates in this region), the liver. Other organs (especially brain and heart) contain CA concentrations high enough to potentially affect the CA level in the systemic blood, if instantly released. However, neither partial removal of the brain nor hypophysectomy, "adrenomedullectomy," Stanniectomy, or urophysectomy had an appreciable impact on stimulated CA release. Together with previous data, these findings show that in the eel (a) the region of the presumed adrenal medulla equivalent is the most important source of all three CAs in systemic plasma; (b) that strong CA-stimulated CA release also occurs outside this region; and (c) that the pituitary, forebrain, and midbrain are not necessary for the CA-stimulated CA release.

Plasma catecholamine concentrations in rainbow trout (Salmo gairdneri) at rest and after anesthesia and surgery

The effects of surgery and anesthesia on concentrations of plasma epinephrine (E), norepinephrine (NE), and dopamine (DA) were investigated in rainbow trout fitted with dorsal aorta cannulae. Baseline catecholamines (CA) concentrations, established in resting rainbow trout, were 1.55 +/- 0.90 pmol/ml (mean +/- SD) for E, 2.07 +/- 1.26 for NE, and 1.33 +/- 0.87 for DA. These values were based on the pooled analyses of five individual fish taken over seven different sampling periods. The E:NE ratio in resting fish was always less than 1.0. In a second experiment, fish were subjected to dorsal aorta cannulation and sequential blood samples were taken immediately after surgery, and 6, 24, and 48 hr later. Plasma E concentrations were 36 times greater than baseline values in the first sample; NE was 15 times greater and DA was 41 times greater. After surgery, plasma concentrations of all CAs fell rapidly but values were still higher than baseline 6 hr after surgery, then were near baseline at 24 and 48 hr after surgery. The E:NE ratio was about 3.0 immediately after surgery, dropped to 1.8 at 6 hr, and was about 1.0 at 24 and 48 hr. In a third experiment, plasma CAs were determined in a group of five animals anesthetized with tricaine methanesulfonate (100 mg/ml) to advanced anesthesia, and then allowed to recover in flowing well water over a 12-hr observation period. Plasma E and NE concentrations in the fish during early anesthesia (1.14 +/- 0.14 min) were not significantly different from preanesthesia values.(ABSTRACT TRUNCATED AT 250 WORDS)

Catecholamine release by catecholamines in the eel does not require the presence of brain or anterior spinal cord

The catecholamine-producing chromaffin cells of the American eel are strongly innervated by fibers, which, by ultrastructural criteria, seem to be cholinergic. However, neither removal of the brain nor removal of the brain combined with extirpation of the anterior spinal cord prevents the release of catecholamines into the circulation by catecholamines. It appears that the chromaffin cells are controlled by both nervous and humoral stimuli, and that at least some of the latter do not require the presence of "preganglionic" innervation.

Epinephrine effects on carbohydrate metabolism in catfish, Ictalurus melas

Epinephrine injection in catfish, Ictalurus melas, induced (a) a rapid hyperglycemia which lasted for more than 5 hr; and (b) a slight immediate decrease of glycogen in liver and muscles (red and white), followed by an increase at 48th hr in the liver. Epinephrine, added in vitro to tissue slices, increased the output of glucose from liver and enhanced the decrease of glycogen seen in controls. Among the other organs, only white muscle showed a greater decrease of glycogen than the controls. These effects are attributed to an increase of glycogen phosphorylase activity induced by the hormone.

Circadian variations of catecholamine levels in brain, heart, and plasma in the eel, Anguilla anguilla L., at three different times of year

The amounts of catecholamine (dopamine, adrenaline, and noradrenaline) in the brain, heart, and plasma of the eel (Anguilla anguilla L.) during a 24-hr period and at three different times of year were determined by using a radioenzymatic method. Seasonal variations of catecholamine average values were found to be different when considering catecholamine levels in the same tissue (one exception: heart levels in May) or the same amine in different tissues. Circadian rhythms of catecholamine levels were evident only in the brain; the maximum amount generally occurred during the light phase. No correlation could be found between the 24-hr variations in the different tissues. The most important variations were phased with the dark-light cycle but were also dependent on the annual cycle.

Hormonal control of glycogenolysis and the mechanism of action of adrenaline in amphibian liver in vitro

In in vitro cultures of liver from Ambystoma mexicanum glycogenolysis was stimulated by adrenaline, glucagon, and vasopressin in a dose-dependent manner. Maximum activity was seen at 10(-6) M hormone while 10(-9) M was without effect. Dibutyryl cyclic AMP (10(-3) M) stimulated glycogenolysis maximally although 10(-5) M had no effect. The glucose release brought about by adrenaline was blocked by the beta-adrenergic antagonist propranolol but not by prazosin or yohimbine which are alpha 1- and alpha 2-adrenergic antagonists. Cyclic AMP concentrations in liver were elevated within 1 min of administration of adrenaline and remained elevated for at least 60 min. Phosphorylase a activity was elevated 10 min after addition of adrenaline and remained elevated for at least 6 hr. The rise in hepatic cyclic AMP concentration and phosphorylase a activity was largely blocked by propranolol. These findings are consistent with adrenaline acting via a beta-adrenergic receptor in A. mexicanum. Glycogenolysis in A. mexicanum liver was stimulated by isoprenaline and phenylephrine and in each case the stimulation was reduced in the presence of propranolol but unaffected by phentolamine. High concentrations of methoxamine, a specific alpha 1-agonist, had no effect upon glycogenolysis. These findings suggest that alpha-adrenergic receptors play no role in regulation of glycogenolysis in A. mexicanum.