Effect of reserpine on the activity of adrenal enzymes involved in the synthesis of adrenaline

1. After administration of reserpine to rats, the tyrosine hydroxylase (TH) and phenylethanolamine-N-methyl transferase (PNMT) activity in their adrenal glands was found to be increased under in vitro conditions.2. The increase in TH activity occurred at 12-18 h after reserpine whereas the PNMT activity increased at 30 hours. Unlike the TH, the increase in PNMT activity did not appear to be neuronally mediated since ganglion blockade by chlorisondamine failed to antagonize the reserpine-induced increase in PNMT activity. The increase in PNMT activity may be a response to increased utilization of catecholamines.3. Hypophysectomy resulted in a diminution of the activities of both enzymes; the activity of TH, but not of PNMT, could be partially restored by reserpine. ACTH restored the activities of both enzymes almost to normal.4. The differential effect of reserpine suggests that the activities of these two enzymes are controlled by different mechanisms.

Effects of corticotrophin and dexamethasone on the levels of corticosteroids, adrenaline and noradrenaline in the adrenal glands of cats

The concentration of adrenaline, noradrenaline and corticosteroids in the adrenal glands of intact cats was studied after administration of corticotrophin (ACTH) or dexamethasone. The animals were treated with ACTH for 3, 7 or 14 consecutive days and killed 3 h (group A) or 24 h (group B) after the last injection. In group A the levels of corticosteroids were significantly increased. Significant decreases were found in group B. A significant decrease in noradrenaline concentration was found in all experiments after administration of both ACTH and dexamethasone. No significant change in the adrenaline level was observed after only 3 days of ACTH or dexamethasone administration, but significant decreases were obtained in both groups after injection of ACTH for 7 to 14 days. These findings suggest that the decrease in adrenal adrenaline may be secondary to the significant and greater decrease in adrenal noradrenaline and that in the intact cat the glucocorticoid levels, although regulating the activity of the adrenal enzyme for methylation of noradrenaline, may not be the only factor involved in the control of adrenaline production by the adrenal gland.

Effect of chronic administration of nicotine on the concentrations of adrenal enzymes involved in the synthesis and metabolism of adrenaline

Chronic administration of nicotine caused an increase in tyrosine hydroxylase and catecholamine concentrations in rat adrenals, but failed to affect adrenal monoamine oxidase, catechol-O-methyl transferase or phenylethanol-amine N-methyl transferase activities.

Catecholamine synthesis and excretion in rats exposed intermittently to cold

Previous findings have shown a turnover of nuclear DNA, a condition related to the functional activity of these cells, in the adrenal medullae of rats intermittently exposed to cold. Striking differences have been observed between various strains of rats, particularly Italico and Wistar rats. In order to evaluate the function of the adrenal medullary cells, the content of catecholamines in the organ and their urinary excretion have been evaluated, with the fluorimetric method, in rats of Italico and Wistar strains kept at room temperature and exposed intermittently to cold. The results show that (i) at room temperature the levels of excretion are lower in Italico than in Wistar rats in spite of the equal amine contents of the adrenal medullae, (ii) the first exposure to cold causes a large increase in the urinary excretion and a decrease of adrenaline and noradrenaline content of the adrenal glands in both strains, (iii) after 3 days the catecholamine content in the organ was higher than normal in Wistar rats, whereas in the Italico strain it continued to decrease, and (iv) a new steady state at higher levels is reached after 20 days of exposure, when not only the catecholamine content but also the urinary excretion is equal in both strains. These differences between the two strains of rats during intermittent cold exposure are discussed in relation to the behaviour of DNA.