Fluorescence assay of tyrosine hydroxylase activity in tissue homogenate

Zusammenfassung Es wird eine Fluoreszenzmethode zur Bestimmung der Tyrosin-Hydroxylase-Aktivität von Homogenat beschrieben, die auf der Spektrofluorometrie der DOPA-Bildung beruht. Die Tyrosin-Hydroxylase-Aktivität von Homogenat der Nebenniere und des Gehirns (Nucleus caudatus) wurde mit dieser Methode gemessen.     

A sensitive and inexpensive high-performance liquid chromatographic assay for tyrosine hydroxylase

Summary We describe a highly sensitive assay method for tyrosine hydroxylase (TH) using high-performance liquid chromatography with amperometric determination. This assay method could be applicable to any tissues with low enzyme activity, such as rat cerebellum. We also describe the kinetic properties of TH in rat cerebral cortex.     

A sensitive and inexpensive high-performance liquid chromatographic assay for tyrosine hydroxylase

We describe a highly sensitive assay method for tyrosine hydroxylase (TH) using high-performance liquid chromatography with amperometric determination. This assay method could be applicable to any tissues with low enzyme activity, such as rat cerebellum. We also describe the kinetic properties of TH in rat cerebral cortex.     

Tyrosine hydroxylase activity and tyrosine titers during cockroach metamorphosis

Summary Tyrosine hydroxylation (TH) to dopa in vivo in nymphs and pharate adults ofPeriplaneta americana was very low, but increased over 30-fold beginning at ecdysis. Free tyrosine increased in pharate, adults and peaked at ecdysis, whereas TH activity peaked 6 h later. Both TH activity and tyrosine titers declined the next 24 h as the cuticle tanned. TH appears to regulate tanning substrate biosynthesis in cockroaches.Contribution No. 81-294-j, Department of Entomology, Kansas Agricultural Experiment Station, Manhattan KS. Research supported in part by National Science Foundation grant No. PCM-8003859. I wish to thank Dr. M.A.J. Al-Izzi for assistance with the enzyme analyses.     

Influence of castration and testosterone replacement on hypothalamic tyrosine hydroxylase activity in the rat

Summary Hypothalamic tyrosine hydroxylase (TH) activity of castrate rats is modulated by testosterone propionate (TP) in vivo. Kinetic studies revealed that bothV _max andK _m were virtually unaltered for substrate tyrosine in the presence of an excess of DMPH₄ cofactor. TP replacement to castrate rats increased theK _m for added DMPH₄ cofactor, whileV _max decreased. These results suggest that TP decreases TH activity of castrate rats by inhibiting the enzymereduced pteridine cofactor complex.     

Influence of castration and testosterone replacement on hypothalamic tyrosine hydroxylase activity in the rat.

Hypothalamic tyrosine hydroxylase (TH) activity of castrate rats is modulated by testosterone propionate (TP) in vivo. Kinetic studies revealed that both Vmax and Km were virtually unaltered for substrate tyrosine in the presence of an excess of DMPH4 cofactor. TP replacement to castrate rats increased the Km for added DMPH4 cofactor, while Vmax decreased. These results suggest that TP decreases TH activity of castrate rats by inhibiting the enzyme-reduced pteridine cofactor complex.     

Hypothalamic tyrosine hydroxylase activity,plasma gonadotropin and prolactin levels after aminooxyacetic acid in ovariectomized rats

Summary Plasma concentrations of gonadotropin, prolactin and hypothalamic tyrosine hydroxylase (TH) activity were measured in ovariectomized rats treated with aminooxyacetic acid (AOAA), a drug which elevates brain GABA levels. Hypothalamic TH activity was significantly increased with a significant decrease in prolactin (Prl) release. Plasma levels of gonadotropins were not modified by AOAA. These results support an inhibitory action of GABA on Prl release possibly mediated through hypothalamic dopamine.Supported by grants from Indian Council of Medical Research (ICMR), New Delhi. RIA kits for the estimation of LH, FSH and Prl were kindly supplied by Dr A.F. Parlow, NIAMDD-NIH, Bethesda, Maryland, USA. GNB is a UGC research fellow.     

Hypothalamic tyrosine hydroxylase activity, plasma gonadotropin and prolactin levels after aminooxyacetic acid in ovariectomized rats

Plasma concentrations of gonadotropin, prolactin and hypothalamic tyrosine hydroxylase (TH) activity were measured in ovariectomized rats treated with aminooxyacetic acid (AOAA), a drug which elevates brain GABA levels. Hypothalamic TH activity was significantly increased with a significant decrease in prolactin (Prl) release. Plasma levels of gonadotropins were not modified by AOAA. These results support an inhibitory action of GABA on Prl release possibly mediated through hypothalamic dopamine.     

Increase in the hypothalamic tyrosine hydroxylase activity after lesion of the catecholaminergic neurons of the rat pontine tegmentum]

Hypothalamic tyrosine hydroxylase activity is increased 6 and 18 h after bilateral lesioning of the Locus Coerulues, in the Rat. An adrenocortical hypertrophy was observed previously, under the same experimental conditions. The neurochemical and neuroendocrinological implications of theses results are discussed.     

Somatic cell hybrids producing inhibitors of melanotic melanoma tyrosine hydroxylase

Summary Splenic lymphocytes from BALB/c mice pre-immunized with purified tyrosine hydroxylase (TH) were fused with murine myeloma N/1 cells. Supernatants of only 2 from large number of cloned cell hybrids contained an inhibitor of TH.     

Quantitative immunofluorescence of tyrosine hydroxylase in the adrenal medulla of spontaneously hypertensive rats

The amount of tyrosine hydroxylase protein in the adrenal medulla, which was estimated by a quantitative immunofluorescence method, was higher in spontaneously hypertensive rats than in normotensive control Wistar-Kyoto rats at 4 and 16 weeks of age before and after the development of hypertension.     

Quantitative immunofluorescence of tyrosine hydroxylase in the adrenal medulla of spontaneously hypertensive rats

Summary The amount of tyrosine hydroxylase protein in the adrenal medulla, which was estimated by a quantitative immunofluorescence method, was higher in spontaneously hypertensive rats than in normotensive control Wistar-Kyoto rats at 4 and 16 weeks of age before and after the development of hypertension.This study was supported by grants from the Ministry of Education, Science and Culture, Japan (No. 59570018). Reprint requests to I.N., Department of Anatomy, School of Medicine, Fujita-Gakuen Health University, Toyoake, Aichi 470-11 (Japan).     

Subcellular distribution of tyrosine hydroxylase and monoamine oxidase in the bovine caudate nucleus

Zusammenfassung Die subzelluläre Lokalisation von Tyrosin-Hydroxylase und Monoaminoxydase im Nucleus caudatus des Rindergehirns wurde untersucht. Tyrosin-Hydroxylase fand sich grösstenteils in den Synaptosomen, den Mikrosomen und dem Zytoplasma. Eine bedeutende Aktivität von Monoaminoxydase war in den Mitochondrien vorhanden.     

Correlation between serum dopamine-beta-hydroxylase activity and dopamine-beta-hydroxylase and tyrosine hydroxylase activities in central and peripheral adrenergic neurons and adrenal glands.

Serum dopamine-beta-hydroxylase activity in spontaneously hypertensive rats and Wistar-Kyoto rats had a positive correlation with dopamine-beta-hydroxylase and tyrosine hydroxylase activities in mesenteric vessels, vas deferens, and adrenal glands at 14-16 weeks of age, a negative correlation with dopamine-beta-hydroxylase activity in locus coeruleus at 3 weeks and 14-16 weeks of age, and a positive correlation with tyrosine hydroxylase activity only at 3 weeks of age, but not at 14-16 weeks of age.     

The effect of high phenylalanine concentration on the formation of DOPA from phenylalanine and tyrosine by tyrosine hydroxylase

Zusammenfassung Auf der Basis gegenseitiger Hemmung von Phenylalanin konnte die enzymatische Bildung des DOPA über Phenylalanin und Tyrosin mittels Tyrosinhydroxylase untersucht werden. Eine 70%ige Hemmung der enzymatischen DOPA-Bildung ergab sich im Fall der dreissigfachen Konzentration des Phenylalanin. Die Möglichkeit einer Hemmung der Norepinephrin-Bildung in Phenylketonurie wird diskutiert.     

Aryl hydrocarbon hydroxylase activity in type II alveolar lung cells

Summary Type II alveolar lung cells metabolize polycyclic aromatic hydrocarbons as indicated by measurements of aryl hydrocarbon hydroxylase activity and binding of tritium labeled benzo(a)pyrene to nuclear and cytoplasmic components.