Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.16.2 (tyrosine hydroxylase)
 14,760 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In situ hybridization histochemistry was used to locate cells containing tyrosine hydroxylase (TH) mRNA in the hypothalami of salt-loaded and Brattleboro rats. The hyperosmotic plasma conditions found in these animals, as compared to control animals, was associated with an increase in detectable TH mRNA-producing cells in the paraventricular and supraoptic nuclei. These results suggest that dopamine synthesized by neurons of those nuclei may participate in the regulation of neuropeptide synthesis and release within the nuclei and the posterior pituitary.
 ...
PMID:Tyrosine hydroxylase mRNA is increased by hyperosmotic stimuli in the paraventricular and supraoptic nuclei. 289 7

Reduction in renal function is a key factor to the development of salt-dependent hypertension; however, the mechanism is obscure. To examine the role of the sympathetic nervous system (SNS) and central catecholaminergic neurons in this predisposition to the development of hypertension, the activity of tyrosine hydroxylase (TH) was determined in SNS and in several brain regions. In another group of unilaterally nephrectomized rabbits, cardiovascular responsiveness to norepinephrine was determined. A unilateral nephrectomy increased the activity of TH in the midmedulla, a brain region important in the baroreflex regulation of blood pressure, and in the adrenal gland, the major source of circulating catecholamines. The activity of TH was decreased in the pons-upper medulla region. No alterations were found in the proximal and distal mesenteric arteries, lower medulla, midbrain or hypothalamus. No alteration in blood pressure or cardiovascular responsiveness to norepinephrine was found. This study indicates that a unilateral nephrectomy produces long-lasting effects on central catecholaminergic neurons and the sympathetic nervous system without an effect on blood pressure or cardiovascular responsiveness.
 ...
PMID:Nephrectomy-induced alterations in the synthesis of catecholamines in the sympathetic nervous system and central nervous system. 289 99

DT diaphorase [NAD(P)H:quinone oxidoreductase] activity was measured in subcellular fractions from homogenates of striatum, frontal cortex, hippocampus, cerebellum, hypothalamus and substantia nigra. This flavoprotein, which by definition oxidizes dihydronicotinamide adenine dinucleotide and dihydronicotinamide adenine dinucleotide phosphate at equal rates and is completely inhibited by 10(-5) M dicoumarol, was found to constitute 80-90% of the total dihydronicotinamide adenine dinucleotide- and dihydronicotinamide adenine dinucleotide phosphate-reductase activities in all brain regions studied. Antibodies raised against purified cytosolic DT diaphorase from the rat liver cross-reacted with the brain enzyme and inhibited soluble DT diaphorase from striatum and cerebellum to 80-90%. Immunohistochemical studies with the same antibodies demonstrated the occurrence of DT diaphorase immunoreactivity in a population of neurons in the substantia nigra and ventral tegmental area. In some neurons there was a colocalization of DT diaphorase and tyrosine hydroxylase-like immunoreactivity. The dense network of DT diaphorase-immunoreactive fibres in the striatum disappeared along with the dopaminergic innervation after 6-hydroxydopamine lesion. DT diaphorase immunoreactivity was also found in Bergmann glia, astrocytes and tanycytes. No correlation appeared to exist between the localization of neuronal DT diaphorase immunoreactivity and the dihydronicotinamide adenine dinucleotide phosphate-diaphorase-like activity, as defined by tetrazolium salt staining, used as a marker for certain peptidergic and cholinergic neurons. However, in, for example, glial cells in the cerebellum, DT diaphorase might contribute or be responsible for the histochemical dihydronicotinamide adenine dinucleotide phosphate-diaphorase activity.
 ...
PMID:Distribution of DT diaphorase in the rat brain: biochemical and immunohistochemical studies. 290 55

To determine if alterations of electrolyte balance or sympathetic nervous system activity are present in Dahl salt-sensitive rats (DS) before the onset of hypertension, we compared electrolyte balances, extracellular fluid volume (inulin space), plasma volume (radiolabeled albumin), and norepinephrine turnover in peripheral tissues (heart and interscapular brown fat) in prehypertensive DS and Dahl salt-resistant rats (DR). Animals were maintained for 5 to 7 days on either a "normal" or high NaCl diet. Tissue norepinephrine turnover was evaluated by measuring the rate at which norepinephrine content decreased following tyrosine hydroxylase inhibition with alpha-methyl-p-tyrosine. Blood pressure was higher (p less than 0.05) in DS (135 +/- 2 [SE] mm Hg) than in DR (129 +/- 2 mm Hg) and was not affected by the diets. Extracellular fluid volume and net Na+ and Cl- balances did not differ between DS and DR. However, plasma volume was greater in DS than in DR (p less than 0.05). In both fat and heart, norepinephrine turnover was decreased by dietary NaCl loading in DR (p less than 0.01), but not in DS. Thus, the tendency of the DS to become hypertensive with high NaCl intake may be related to the combined effects of an increased plasma volume and the failure of high dietary NaCl to inhibit peripheral sympathetic nervous system activity.
 ...
PMID:Failure of salt loading to inhibit tissue norepinephrine turnover in prehypertensive Dahl salt-sensitive rats. 320 61

Distinct differences in central and peripheral noradrenaline (NA) were observed in the hypertension prone (SBH) and resistant (SBN) strain, derived from the Hebrew University SABRA rats. In the medulla oblongata NA concentration was 90% higher and tyrosine hydroxylase activity 88% lower in SBN when compared to SBH, suggesting marked strain differences in NA turnover. In this area, NA-induced cAMP generation was higher in SBH than in SBN, while the hypothalamus, the reverse situation was present. The relevance of hypertension of the reciprocal cAMP changes is still uncertain. The concentration of NA in heart tissue was significantly higher in SBN than in SBH. Doca-salt treatment caused hypertension and depletion of atrial NA in SBH, but had no effect on either blood pressure or atrial NA in SBN rats. The results suggest that resistance to hypertension in SBN rats is associated with decreased NA turnover in medulla oblongata and reduced activity of cardiac neuronal sympathetic endings.
 ...
PMID:Distinguishing traits in the Sabra hypertension-prone (SBH) and hypertension-resistant (SBN) rats. 611 32

By selective inbreeding of the Hebrew University Sabra rat, we have obtained a hypertension prone (H) and a hypertension resistant (N) substrain. The criteria for selection was the blood pressure response to DOCA-salt. The outstanding element of our model is the N rat with its remarkable resistance to hypertension. When compared to H, the N rat presents the following characteristics: 1. The blood pressure of experimentally naive N rats is significantly lower at comparable ages, in both sexes. 2. N rats are resistant to both DOCA-salt and renal clip hypertension. 3. In the medulla oblongata (MO) of N rats, the noradrenaline (NA) content is significantly higher and the activity of tyrosine hydroxylase is significantly lower. 4. In the MO of N rats, the sensitivity of the NA dependent cAMP generating system is significantly decreased. 5. In the atrium of N rats, the NA content is significantly higher, and is unaffected by DOCA-salt treatment. The results suggest that genetic differences in catecholamine metabolism may account for the disparate susceptibility to hypertension of the two strains.
 ...
PMID:The Sabra hypertension prone (H) and hypertension resistant (N) rat strain. 612 Apr 96

The properties of purified tyrosine hydroxylase (TH) from bovine corpus striatum, both native and phosphorylated forms of the enzyme, were studied. TH had a tendency toward greater affinity for tetrahydrobiopterin (BH4) than for the synthetic cofactor 6-methyltetrahydropterin (6-MPH4), although the maximal velocity of the TH-catalyzed reaction was greater with 6-MPH4. Phosphorylation increased the affinity of TH for cofactor at pH 6.0, with little change in Vmax. At pH 7.0, phosphorylation caused increased activation of TH by increasing Vmax as well as reducing the Km for cofactor. The K1 for dopamine was increased twofold by phosphorylation at pH 6.0, but eightfold at pH 7.0. Phosphorylation was not associated with a change in Km for tyrosine at any pH or with any cofactor studied, although the Km for tyrosine of TH was cofactor-dependent and seven to eight times greater with 6-MPH4 than with BH4 as cofactor. Heparin and NaCl activated native TH at pH 6.0, but not at pH 7.0. Phosphorylated TH was unaffected by heparin or salt at pH 6.0, but was relatively inhibited at pH 7.0. The data are presented in the context of the physiological environment of TH.
 ...
PMID:Tyrosine hydroxylase from bovine striatum: catalytic properties of the phosphorylated and nonphosphorylated forms of the purified enzyme. 612 57

Catecholamine levels and activity of catecholamine-forming enzymes have been quantitated in adrenal glands of Dahl sodium-resistant (R) and sodium-sensitive (S), genetically hypertensive rats maintained on low- or high-salt diets. A high-salt diet results in markedly different changes in the catecholamine metabolism in R and S rats. In R rats, a high-salt diet reduces the activities of tyrosine 3-hydroxylase (TH;-5%) and dopamine beta-hydroxylase (DBH; -18%) as well as the levels of all catecholamines (dopamine -28%, norepinephrine -11%, and epinephrine -28%). In contrast, S rats fed a high-salt diet showed increased TH (+7%) and phenylethanolamine N-methyltransferase (+16%) activities as well as an increased content of adrenal norepinephrine (+13%) and epinephrine (+21%). These findings demonstrate a genetic difference in the effects of a high-salt diet on the synthesis of catecholamines in the adrenal gland of Dahl R and S rats. Hypertension only occurs in S rats on a high-salt diet, concomitant with large increases in the formation of adrenal catecholamines.
 ...
PMID:Increased adrenal catecholamines in salt-sensitive genetically hypertensive Dahl rats. 613 26

We examined by immunohistochemistry the effect of salt loading on the expression of tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC), and GTP cyclohydrolase I (GCH) in Purkinje cells of the mouse cerebellum. In control mice, only a few Purkinje cells were positive for TH or AADC. No Purkinje cells were stained for GCH. Drinking 2% sodium chloride for 2 weeks resulted in an increase in the number of TH- or AADC-positive Purkinje cells in the caudal vermis, paraflocculus and flocculus of the cerebellum. In contrast, no Purkinje cells were immunoreactive to GCH or L-DOPA after the salt loading. The present findings suggest that the salt loading differentially affects the expression of TH, AADC and GCH in Purkinje cells of the mouse cerebellum.
 ...
PMID:Enhanced expression of tyrosine hydroxylase and aromatic L-amino acid decarboxylase in cerebellar Purkinje cells of mouse after hyperosmotic stimuli. 747

With in situ hybridization we examined the localization of mRNA coding for tyrosine hydroxylase (TH) in the rat hypothalamo-neurohypophysial system (HNS) under conditions of acute osmotic stress. Fifteen min after salt loading, hybridization signal of TH mRNA could be located in the magnocellular hypothalamic nuclei and in the median eminence (ME). In untreated animals, TH mRNA was detected only in the ME. In osmotically challenged animals that had been pretreated with colchicine, signals for TH mRNA remained confined to the ME, while pretreatment of salt loaded rats with a polymerase II transcription inhibitor resulted in labelling of the magnocellular perikarya but a decrease of the hybridization signal in the ME. Our results suggest that also TH mRNA is among the RNAs which are axonally transported in the HNS. TH mRNA can probably be stored in axons of the hypothalamo-neurohypophysial tract, to be transported retrogradely and translated upon certain stimuli.
 ...
PMID:Localization of tyrosine hydroxylase mRNA in the axons of the hypothalamo-neurohypophysial system. 751 30


<< Previous 1 2 3 4 5 6 7 Next >>