L.B. Geffen

Serum dopamine β-hydroxylase as an index of sympathetic function

Publisher Summary This chapter describes the serum dopamine 3-hydroxylase (DBH) as an index of sympathetic function. DBH is a copper-containing mixed function oxidase that catalysis hydroxylation of the three carbon in the side chain of phenylethylamine derivatives. The enzyme has been tentatively characterized as a tetrameric glycoprotein with 1 or 2 active sites, each containing one copper molecule that undergoes cyclic oxidation and reduction. It has a molecular weight of close to 290,000. Under dissociating conditions, four subunits of molecular weight 75,000 have been reported but it is uncertain whether the units are identical or catalytically active. Enzymatic activity may depend upon the cooperative action of two or even all four subunits, and upon sugar residues that comprise 4% of the molecule. Amino acid analysis has revealed that DBH is a highly acidic protein, rich in glutamate and aspartate, and deficient in methionine and half-cystine. The enzyme requires molecular oxygen and a reducing agent as cofactors. Ascorbate is generally used to reduce the enzyme in vitro but can be replaced by dimethyltetrahydropterine. Pterines may therefore play a similar regulatory role to that proposed in the first rate-limiting step in catecholamine synthesis catalyzed by tyrosine hydroxylase.

Immune lesions of central noradrenergic neurons produced by antibodies to dopamine-β-hydroxylase

(1) Intraventricular injection of antibodies to dopamine-beta-hydroxylase (DBH) caused degeneration of central noradrenergic nerve terminals in rats and guinea-pigs. In rats it was necessary to infuse exogenous complement in the form of guinea-pig serum together with the anti-DBH, whereas in guinea-pigs the anti-DBH was effective on its own. Control animals were infused with equivalent amounts of non-immune serum and complement and showed no signs of degeneration other than in the region of the needle tract. (2) There was a loss of varicosities in most terminal fields of the noradrenergic projections and swollen distorted axons were seen in both ascending and descending noradrenergic pathways. Noradrenergic cell bodies in the locus coeruleus and subcoeruleus appeared unaffected. No histochemical changes were observed in dopaminergic neurons. (3) The ultrastructural changes in degenerating axons that were first identifided by fluorescence histochemistry included swelling, vacuolation, accumulation of dense cored vesicles, lysosome-like bodies and smooth membranous sacs. The surrounding neuropil appeared normal. (4) There was a significant depletion of noradrenaline in all regions of the rat brain ranging from 20% in the hypothalamus to 80% in the neocortex. Dopamine concentrations were unaffected. (5) These observations provide a new approach to the production of selective lesions in specific neurotransmitter pathways that could be extended to non-adrenergic neurones. They may also be useful as a model for the study of autoimmune diseases of the nervous system.

Effect of nerve activity on transport of nerve growth factor and dopamine β-hydroxylase antibodies in sympathetic neurones

The effect of nerve activity on the uptake and retrograde transport of nerve growth factor (NGF) and dopamine beta-hydroxylase (DBH) antibodies was studied by injecting 125I-labelled NGF and anti-DBH into the anterior eye chamber of guinea-pigs. Decentralization of the ipsilateral superior cervical ganglion (SCG) had no significant effect on the retrograde transport of either NGF or anti-DBH. Phenoxybenzamine produced a 50% increase in anti-DBH but not NGF accumulation and this effect was prevented by prior decentralization. This demonstrates that NGF is taken up independently of the retrieval of synaptic vesicle components.

Galanin-containing fibers innervate substance P-containing neurons in the pedunculopontine tegmental nucleus in humans

Galanin is a putative peptide transmitter distributed widely in the central nervous system. Galanin shows potent inhibitory effects on neuronal activity and learning behaviors induced or mediated by acetylcholine. Here, we demonstrate that in humans there are abundant galanin-containing fibers in the pedunculopontine tegmental nucleus, the lateral dorsal tegmental nucleus and the oral pontine reticular nucleus. These neurons contain both acetylcholine and substance P (SP). Using a double-immunostaining method, we show that galanin-containing terminals from pericellular baskets around many SP-positive neurons in these nuclei. Our results suggest galanin may influence brain functions via inputs to the ascending mesopontine acetylcholine-containing nuclei.

USE OF DOPAMINE β-HYDROXYLASE IN THE STUDY OF VESICLE DYNAMICS

ABSTRACT The binding of locally administered antibodies to dopamine β-hydroxylase (DBH) was used to study the dynamics of vesicle membranes exposed on plasma membranes during exocytosis in sympathetic nerves. In guinea-pigs binding of anti-DBH was shown to lead to a complement-mediated lysis of noradrenergic nerve terminals. In the absence of complement binding, degeneration does not occur; instead the antibody is taken up and transported retrogradely. The fate of DBH in vesicles that have undergone exocytosis has been studied by the use of immunohistochemical and immunocytochemical localization of DBH antibodies.

Dopamine-β-hydroxylase activity in plasma obtained from the pulmonary artery and left ventricle of man

Abstract Dopamine-β-hydroxylase activity (DBH) has been measured in plasma obtained simultaneously from the pulmonary artery and left ventricle of fourteen patients who underwent diagnostic cardiac catheterisation. In the majority of these subjects the levels of enzyme activity in the arterial and venous blood were similar, indicating that inactivation of DBH had not occurred in its passage through the pulmonary circulation. One patient with pulmonary hypertension had a large a-v difference in enzyme activity that may have been caused by altered pulmonary haemodynamics. Three of the five subjects that undertook a standardised exercise test on a bicycle ergometer showed a significant increase in plasma DBH activity. There was no correlation between the increases in DBH activity and in cardiac index and heart rate.

IMMUNE LESIONS OF CENTRAL NORADRENERGIC NEURONS PRODUCED BY DOPAMINE β-HYDROXYLASE (DBH) ANTIBODIES

ABSTRACT Intraventricular injection of DBH antibodies together with complement caused widespread degeneration of noradrenergic nerves in rat and guinea-pig brain. DBH antibodies were also taken up by noradrenergic nerves and transported retrogradely to their cell bodies. The specificity of the lesions was demonstrated by histochemistry, biochemistry and electron microscopy. Administration of DBH antibodies in vivo provides a useful tracing and lesioning tool as well as a potential model for autoimmune neurological diseases.

SERUM DOPAMINE β-HYDROXYLASE AS AN INDEX OF SYMPATHETIC FUNCTION

Publisher Summary This chapter describes the serum dopamine 3-hydroxylase (DBH) as an index of sympathetic function. DBH is a copper-containing mixed function oxidase that catalysis hydroxylation of the three carbon in the side chain of phenylethylamine derivatives. The enzyme has been tentatively characterized as a tetrameric glycoprotein with 1 or 2 active sites, each containing one copper molecule that undergoes cyclic oxidation and reduction. It has a molecular weight of close to 290,000. Under dissociating conditions, four subunits of molecular weight 75,000 have been reported but it is uncertain whether the units are identical or catalytically active. Enzymatic activity may depend upon the cooperative action of two or even all four subunits, and upon sugar residues that comprise 4% of the molecule. Amino acid analysis has revealed that DBH is a highly acidic protein, rich in glutamate and aspartate, and deficient in methionine and half-cystine. The enzyme requires molecular oxygen and a reducing agent as cofactors. Ascorbate is generally used to reduce the enzyme in vitro but can be replaced by dimethyltetrahydropterine. Pterines may therefore play a similar regulatory role to that proposed in the first rate-limiting step in catecholamine synthesis catalyzed by tyrosine hydroxylase.