Effects of adrenaline administration on the interrenal gland of the newt,Triturus carnifex: Evidence of intraadrenal paracrine interactions

Chronic exposure to cadmium disrupts the adrenal gland activity of the newt Triturus carnifex (Amphibia, Urodela)

We intended to verify the safety of the freshwater values established for cadmium by the European Community and the Italian Ministry of Health in drinking water (5 μg/L) and sewage waters (20 μg/L). Therefore, we chronically exposed the newt Triturus carnifex to 5 μg/L and 20 μg/L doses of cadmium, respectively, during 3 and 9 months and verified the effects on the adrenal gland. We evaluated the serum concentrations of adrenocorticotropic hormone (ACTH), corticosterone, aldosterone, norepinephrine, and epinephrine. During the 3-month exposure, both doses of cadmium decreased ACTH and corticosterone serum levels and increased aldosterone and epinephrine serum levels. During the 9-month exposure, the 5 μg/L dose decreased ACTH and increased aldosterone and epinephrine serum levels; the 20 μg/L dose decreased norepinephrine and epinephrine serum levels, without affecting the other hormones. It was concluded that (1) chronic exposure to the safety values established for cadmium disrupted the adrenal gland activity and (2) the effects of cadmium were related both to the length of exposure and the dose administered. Moreover, our results suggest probable risks to human health, due to the use of water contaminated by cadmium.

The autonomic nervous system and chromaffin tissue: neuroendocrine regulation of catecholamine secretion in non-mammalian vertebrates

If severe enough, periods of acute stress in animals may be associated with the release of catecholamine hormones (noradrenaline and adrenaline) into the circulation; a response termed the acute humoral adrenergic stress response. The release of catecholamines from the sites of storage, the chromaffin cells, is under neuroendocrine control, the complexity of which appears to increase through phylogeny. In the agnathans, the earliest branching vertebrates, the chromaffin cells which are localized predominantly within the heart, lack neuronal innervation and thus catecholamine secretion in these animals is initiated solely by humoral mechanisms. In the more advanced teleost fish, the chromaffin cells are largely confined to the walls of the posterior cardinal vein at the level of the head kidney where they are intermingled with the steroidogenic interrenal cells. Catecholamine secretion from teleost chromaffin cells is regulated by a host of cholinergic and non-cholinergic pathways that ensure sufficient redundancy and flexibility in the secretion process to permit synchronized responses to a myriad of stressors. The complexity of catecholamine secretion control mechanisms continues through the amphibians, reptiles and birds although neural (cholinergic) regulation may become increasingly important in birds. Discrete adrenal glands are present in the non-mammalian tetrapods but unlike in mammals, there is no clear division of a steroidogenic cortex and a chromaffin cell enriched medulla. However, in all groups, there is an obvious intermingling of chromaffin and steroiodogenic cells. The association of the two cell types may be particularly important in the amphibians and birds because like in mammals, the enzyme catalysing the methylation of noradrenaline to adrenaline, PNMT, is under the control of the steroid cortisol.

The adrenal gland of newt Triturus carnifex (Amphibia, Urodela) following in vivo betamethasone administration

The response of the adrenal gland of Triturus carnifex to betamethasone administration was studied; the effects were evaluated by examination of the ultrastructural morphological features of the tissues as well as the serum levels of aldosterone, corticosterone, norepinephrine and epinephrine. In March and June, betamethasone significantly decreased the serum levels of aldosterone and corticosterone and the lipid droplet content in the steroidogenic cells. Moreover, betamethasone influenced the chromaffin tissue, enhancing in March (when the chromaffin cells produce norepinephrine and epinephrine in almost equal quantities) epinephrine serum levels and the numeric ratio between norepinephrine and epinephrine granules in the chromaffin cells. In June, (when the chromaffin cells contain almost exclusively norepinephrine granules) betamethasone administration raised norepinephrine serum levels, whereas a decrease in the numeric ratio between norepinephrine and epinephrine granules in the chromaffin cells was found. Finally, betamethasone administration did not evoke in June any increase in the mean number of epinephrine granules in the chromaffin cells and/or in epinephrine serum levels, as would be expected if phenyletanolamine-N-methyl transferase (PNMT) enzyme, converting norepinephrine into epinephrine, were activated by corticosteroids. The results of this study showed that betamethasone decreased aldosterone and corticosterone serum levels and enhanced catecholamine serum concentrations. Moreover, the present results suggest that a stimulatory role of glucocorticoids on PNMT enzyme may be ruled out.