Norepinephrine-Synthesizing Enzymes in Brain, Adrenals and Peripheral Sympathetic Nerves of Spontaneously Hypertensive Rats

Abstract

Abstract-Dopamine-,;7-hydroxylase (DBH) activity in serum, DBH and tyrosine hydroxylase (TH) activities in mesenteric vessels, and DBH and TH activities in locus coeruleus and hypothalamus of brain did not differ significantly between spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKR) at 16 weeks of age when hypertension of SHR was fixed. In contrast, DBH and TH activities in vas deferens and adrenal glands were significantly higher in SHR than in WKR. These changes in SHR at 16 weeks of age after establishment of hypertension are directly opposite those reported previously in SHR at 3 weeks of age before the onset of hyper tension.We have previously reported (1, 2) that dopamine-;3-hydroxylase (DBH) activity in young spontaneously hypertensive rats (SI-I R) (3) was increased in serum and mesenteric vessels and was decreased in the locus coeruleus area of the brain. These results suggest that the sympathetic nerve activity may be increased in blood vessels due to a low norad rencrgic activity in the brainstem of young SHR before the onset of hypertension. During the development and maintenance of hypertension in SHR from 6 to 53 weeks of age, serum DBH activity in SHR was found to be similar to that in control normotensive Wistar-Kyoto rats (WKR) (1), suggesting that the peripheral sympathetic nerve activity may be decreased to the level of normotensive WKR by a compensatory mechanism.We investigated DBH activity in serum, and DBH and tyrosine hydroxylase (TH) activities in mesenteric vessels, vas deferens, adrenals and ca tech olaminergic regions of brain in SHR and WKR at 16 weeks of age when the hypertension is fixed, in order to compare the activity of the peripheral sympathetic nerves, adrenal glands and catechola ininergic neurons of the brain.

Markedly elevated specific renin levels in the adrenal in genetically hypertensive rats.

“…Thus, whether the effect of the increased renin in the cortex is limited to the cortex or extends to the medulla remains to be clarified. The increased function ofcatecholamine synthesis in the adrenal of SHR (3,30) is compatible with the increased medullary renin and with a possible corticomedullary interaction (48)(49)(50) of cortical' renin.…”

“…The increased level of adrenal renin in young and adult SHR and the gradual decrease with age find a parallelism in similar but less pronounced changes in adrenal dopamine ,8-hydroxy-lase of SHR (3,30) and suggest a possible link between the adrenergic system during the development and the early maintenance phase ofhypertension. However, a contrary observation of decreased levels of adrenergic enzyme systems.…”

Effects of ethanol on catecholamine levels and related enzyme activities in different brain regions of rats.

“…Determination of tyrosine hydroxylase activity: TH activity was determined by measuring 14C-dopy formed from 14C_ tyrosine principally according to the method of Nagatsu et al (5). Tissue pieces were homogenized in 3 ml of chilled 0.05 M tris HCI buffer, pH 6.0, containing 0.2% Triton (7) using an ammonia electrode.…”