The activities of catecholamine-synthesizing enzymes in adrenal glands have been investigated during the development of high blood pressure in spontaneously hypertensive rats (SHR) and in rats made hypertensive by administration of DOCA and saline. There was a significant decrease in the activity of tyrosine hydroxylase, dopamine-/?-hydroxylase, and phenylethanolamine N-methyltransferase in you...

The precise mechanisms by which beneficial responses to acute stress are transformed into long-term pathological effects of chronic stress are largely unknown. Western blot analyses revealed that members of the AP1 transcription factor family are differentially regulated by single and repeated stress in the rat adrenal medulla, suggesting distinct roles in establishing stress-induced patterns o...

The hydroxylase cofactor, tetrahydrobiopterin, and its biosynthetic system are localized in dopaminergic nerve terminals in the striatum. This conclusion is based on the nearly equivalent loss of tyrosine hydroxylase and tetrahydrobiopterin and its initial biosynthetic enzyme, guanosine triphosphate cyclohydrolase, after injection of 6-hydroxydopamine into the substantia nigra. The role of the ...

Disappearance rates of intracisternally administered H-norepinephrine and activities of tyrosine hydroxylase were examined in the rabbit in five brain regions (telencephalon, hypothalamus, midbrain, medulla-pons, and cerebellum) and in three cord regions (cervical, thoracolumbar, and lumbosacral) 2 weeks after section of the carotid sinus and aortic nerves. Mean blood pressure rose by 29% and h...

The genome of the protozoan parasite Toxoplasma gondii was found to contain two genes encoding tyrosine hydroxylase; that produces L-DOPA. The encoded enzymes metabolize phenylalanine as well as tyrosine with substrate preference for tyrosine. Thus the enzymes catabolize phenylalanine to tyrosine and tyrosine to L-DOPA. The catalytic domain descriptive of this class of enzymes is conserved with...

We have recently shown that chronic fluoxetine treatment acted significantly increasing plasma norepinephrine and epinephrine concentrations both in control and chronically stressed adult male rats. However, possible effects of fluoxetine on catecholamine synthesis and re-uptake in adrenal medulla have been largely unknown. In the present study the effects of chronic fluoxetine treatment on tyr...

Three different methods for the determination of phenylalanine hydroxylase activity have been compared: a) Differential photometric assay of the increase in tyrosine concentration in the presence of phenylalanine; b) Product separation by thin layer chromatography and scintillation counting of the [14C]tyrosine formed; c) HPLC separation and spectrofluorometric quantification of derivatized ami...

Although it is clear that cardiac norepinephrine stores are often markedly reduced in congestive heart failure, the mechanism responsible for this depletion has not been elucidated. The objective of this study was to investigate cardiac synthesis of norepinephrine in experimental right-sided heart failure by measuring the activity of tyrosine hydroxylase, the rate-limiting enzyme in the biosynt...

Inflammation, phospho-p38 MAPK activation, and a reduction in glial cell line-derived neurotrophic factor (GDNF) occur in Parkinson's disease. Microglial activation in the substantia nigra and a tyrosine hydroxylase deficit in the striatum of 3-month-old GDNF heterozygous (GDNF(+/-)) mice were previously reported and both were exacerbated by a toxic methamphetamine binge. The current study asse...

The properties of partially purified tyrosine hydroxylase from six pheochromocytomas were compared with partially purified normal human and bovine adrenal medulla enzyme. Substrate and inhibition kinetics, cofactor requirements, and intracellular localization of the enzyme from normal and tumor chromaffin tissue of humans were similar, as was the amount of enzyme activity per gram of tissue. Co...