Influence of cold exposure and thyroid hormones on regulation of adrenal catecholamines

Abstract

Since thyroid hormones influence urinary excretion of catecholamines after exposure to cold, the effects of hyper- and hypo-thyroidism on adrenal tyrosine hydroxylase (TH) (EC 1.14.16.2), phenylethanolamine-N-methyl transferase (PNMT) (EC 2.1.1.28), and serum dopamine-beta-hydroxylase (DbetaH) (EC 1.14.17.1) of rats of 23 and 4 degrees C were studied. TH changes resembled the urinary excretion pattern at 4 degrees C in being higher after 8 days than after 1 day of exposure, and in declining as acclimation occurred. At 23 degrees C, TH activity of hypothyroid rats was significantly higher than in euthyroid or hyperthyroid animals, and after 1 day at 4 degrees C the value increased even more. While in the hypothyroid animals at 4 degrees C the concentration of adrenal catecholamines was less, the epinephrine to norepinephrine ratio was higher than at 23 degrees C. Very high TH activity with a decline in catecholamine concentration suggests that the capacity of TH had been exceeded. PNMT activity was significantly elevated in this group. TH activity was not decreased in the hyperthyroid group at 23 degrees C, and was increased after 8 days at 4 degrees C, suggesting that circulating thyroid hormones have no direct inhibitory effect on TH. Serum DbetaH was elevated after exposure to 4 degrees C, regardless of thyroid hormonal status. The activation of adrenal TH in hypothyroid rats at 23 degrees C and of TH, PNMT, and serum DbetaH at 4 degrees C is probably the result of increased activity of the sympathetic nervous system.

Tyrosine Hydroxylase Activity and Catecholamine Content in the Adrenals of Young Hypo- and Hyperthyroid Rats

“…In his extensive review, Harrison (7), summarizing many results, concluded that hyperthyroidism was followed in most cases by a decreased adrenaline content in adrenals. In more recent publications, an increased adrenal catechol amine content (;ug/g of adrenals) and an in creased catecholamine turnover, were described in hypothyroidism, while hyperthyroidism seemed to have no effect on such steps of catecholamine metabolism (10,11). The activ ity of adrenal tyrosine hydroxylase (TH), the enzyme which catalyzes the rate-limiting step in catecholamine biosynthesis (8), has also been shown to be modulated by thyroid hormones, but the results in this field are still conflicting.…”

“…According to Zenker et al (13) and de Grinial et al (2), hypothyroidism induces in the adult rat a decrease in TH activity when expressed per pair of adrenals, while no change was observed when the activity is expressed per unit of protein contents. On the other hand, R oy et al (10) found that hypothyroidism is associ ated with an enhanced TH activity (expressed per unit of protein contents) while hyperthy roidism has no effect on this activity.…”

Catecholamine-Related Gene Expression Correlates With Blood Pressures in SHR

“…5 Adrenergic chromaffin cells appear to be regulated by cold exposure and glucose deprivation, at least in the rat. 6 Both noradrenaline and adrenaline act at G protein-coupled receptors of the adrenergic receptor family, comprising ␣ 1 , ␣ 2 , or ␤, to mediate sympathetic effects. 7 Within this main classification, there are several subtypes ␣ 1A , ␣ 1B , ␣ 1D , ␣ 2A , ␣ 2B , ␣ 2C , ␤ 1 , ␤ 2 , and ␤ 3 .…”

Evolution of Plasma Dopamine-Beta-Hydroxylase in Hypo- and Hyperthyroid Young Rats

“…In the adult rat, the influence of altered thyroid status is controversial: an increase in DBH activity in hypothyroidism and a de crease in hyperthyroidism have been de scribed [20] as well as no modification of this activity [17]; differences in the technical pro cedures may explain such a discrepancy. Our results, concerning both the 30-day-old rats and the adults, only show an effect of hypo thyroidism.…”

“…21]. Among these, the thyroid state can play a role in the modulation of scrum DBH: in the rat, as well as the human, the enzymatic activity either is not modified [17] or is increased by hypothy roidism and decreased by hyperthyroidism [13,14,20], We previously found various modifica tions in the development of catecholamine metabolism in different organs of hypo-and hyperthyroid young rats, for example in the catecholamine content and activities of some enzymes of catecholamine biosynthesis or degradation [3][4][5].…”