A.F. De Schaepdryver

Release of dopamine β-hydroxylase and chromogranin A upon stimulation of the splenic nerve

Two proteins present in noradrenergic vesicles of the splenic nerve (dopamine beta-hydroxylase and chromogranin A) are released into the perfusate from the spleen when the splenic nerve is stimulated. Experiments in which drugs were added to the perfusion fluid showed that the proteins were released from terminals of the splenic nerve. There was a correlation between the amounts of the proteins released and the quantity of noradrenaline released; and the release process was dependent upon calcium. It is suggested that the proteins are released from the large dense-cored vesicles present in the terminals of the splenic nerve, and that secretion from these vesicles occurs by exocytosis.

Subcellular fractionation of splenic nerve: ATP, chromogranin A and dopamine β-hydroxylase in noradrenergic vesicles

The subcellular particles in axons of the splenic nerve have been studied by centifrugation techniques. By differential centifrugation, five different types of particle could be distinguished and partly separated: noradrenaline-containing particles (noradrenergic vesicles), large and small lysosomes, mitochondria, and microsomal particles. In density gradient centrifugation, only one type of noradrenergic vesicle could he demonstrated. The noradrenergic vesicles and the mitochondria contain ATP. Two proteins (chromogranin A and dopamine beta-hydroxylase) are present in the noradrenergic vesicles.

The presence of dopamine β-hydroxylase in the cerebrospinal fluid of rabbits and its increased concentration after stimulation of peripheral nerves and cold stress

The presence of dopamine beta-hydroxylase activity in the cerebrospinal fluid of rabbits has been shown using a sensitive radiochemical assay; the identity of the reaction product was confirmed by using thin layer chromatographic techniques. The enzyme found in this fluid has some properties (sedimentation and electrophoretic migration) in common with the best characterized preparation of dopamine beta-hydroxylase, that prepared from bovine adrenal chromaffin granules. It also has these properties in common with the enzyme present in the high-speed supernatants obtained from osmotically disrupted synaptosomes prepared from rabbit brain. When the sciatic nerves of rabbits under urethane anaesthesia were stimulated, or when shaved rabbits were subjected to cold stress, the level of dopamine beta-hydroxylase in the cerebrospinal fluid increased. The increase in response to nerve stimulation was gradual, starting within 90 min of stimulation and remained high for at least 3 h after the stimulation had ended, at which time it was 280% of the normal value. There was no equivalent increase in the protein concentration of the cerebrospinal fluid nor was there a change in the enzyme activity when sciatic nerves were exposed but not stimulated. The enzyme present in the cerebrospinal fluid during this period of high activity is identical in its sedimentation and electrophoretic properties to that present in normal fluid. It is suggested that the dopamine beta-hydroxylase activity in cerebrospinal fluid may be derived from noradrenergic neurons within the brain and that the enzyme is released together with noradrenaline.

Tyramine does not release noradrenaline from splenic nerve by exocytosis.

SummaryThe release of noradrenaline by tyramine from bovine splenic nerves was found to be dose dependent. No dopamine-β-hydroxylase could be detected in perfusates from tyramine stimulated spleens in contrast to results obtained by electrical stimulation. It is concluded that the releasing action of tyramine differs fundamentally from that of electrical stimulation in that exocytosis is not involved.

Thin layer chromatography of catecholamines and their metabolites.

Eine einfache, schnelle und empfindliche Methode zur dünnschichtchromatographischen Trennung von 0,2–1µg Menge von Noradrenalin, Adrenalin, Normetanephrin, Metanephrin, 3,4-Dihydroxy-mandelsäure und 3-Methoxy-4-hydroxymandelsäure wird beschrieben.

Estimation of plasma catecholamines in man.

Abstract The influence of body posture and muscular exercise on plasma noradrenaline and adrenaline concentrations was studied in man. The radiometric method of Passon and Peuler (Passon, Ph. and Peuler, J. (1973) Anal. Biochem. 51, 618) was used with slight modifications. With rigorous standardisation of sampling and storage procedures, reproducible results were obtained. Basal values of plasma catecholamines in man can be obtained from subjects after 30 min of rest in the supine position.

The metabolic fate of nitroglycerin (trinitrin) in relation to its vascular effects.

Abstract The metabolism of nitroglycerin (trinitrin) was studied in dogs and rabbits. After intravenous injection of nitroglycerin in either species, plasma levels immediately declined and then gradually increased; maximum plasma levels occurred between 10 and 20 min after injection. This peculiar course of the plasma levels was due to redistribution of the drug in different organs. The blood pressure responses to nitroglycerin did not parallel the plasma levels. Pretreatment of rabbits with SKF 525 A, an enzyme inhibitor, or with phenobarbital, an enzyme inducer, markedly influenced the plasma levels but did not affect the vascular effects of nitroglycerin. After oral administration of nitroglycerin, blood pressure was normal despite high plasma levels. The vascular effects of nitroglycerin did not seem to be determined by its metabolism or plasma levels.

Randomized trial of two beta-mimetic drugs (ritodrine and fenoterol) in acute intra-partum tocolysis

The Paul Martini Prize of DM 20,000 is awarded in remembrance of Professor Paul Martini in appreciation of his contributions to the promotion of clinical therapeutical research. The papers submitted must be self-contained, and published papers must not be older than two years. The papers should be submitted either in German or English to the Medizinisch Pharmazeutische Studiengesellschaft e.V., Bilhildisstrasse 2, D-6500 Mainz, where further information about the presentation will be available. The deadline for submission is April 28, 1981.

The effect of drugs on the concentration of dopamine β-hydroxylase in the cerebrospinal fluid of rabbits

Abstract Systemic administration of each of the drugs studied (phenoxybenzamine, yohimbine, phentolamine, nicotine, physostigmine and pentylenetetrazol) caused an increase in the dopamine β-hydroxylase activity per unit volume of cerebrospinal fluid. The increase was gradual starting within 90 min after injection of the drug and remained high for at least 3 h. At that time the dopamine β-hydroxylase levels after treatment with phenoxybenzamine and yohimbine reached values of 600% and 580%, respectively, of the control. The increase in dopamine β-hydroxylase activity upon phenoxybenzamine treatment was dose dependent. Injection of pentylenetetrazol caused an increase in dopamine β-hydroxylase to 230% of the control value. Pretreatment of rabbits with an intracisternal injection of 6-hydroxydopamine not only caused a 68% decrease in the noradrenaline content and a 69% decrease in the dopamine β-hydroxylase levels in the brain, but also led to a 52% fall in the dopamine β-hydroxylase level of the cerebrospinal fluid. Upon injection of pentylenetetrazol into rabbits pretreated with 6-hydroxydopamine, the dopamine β-hydroxylase levels in the cerebrospinal fluid only reached a mean value of 0.98 units/ml compared with 2.62 units/ ml for control rabbits injected with pentylenetetrazol; the increase in the blood level of dopamine β-hydroxylase activity was, however, unaffected. Data derived from normal and 6-hydroxydopamine pretreated rabbits revealed a fairly good correlation between dopamine β-hydroxylase levels in the cerebrospinal fluid and the brain. From these experiments it is concluded that dopamine β-hydroxylase activity in the cerebrospinal fluid is derived from central noradrenergic neurons and that drugs which increase central noradrenergic activity also increase dopamine β-hydroxylase levels in the cerebrospinal fluid. It is further suggested that determination of dopamine β-hydroxylase activity in the cerebrospinal fluid may be a sensitive and relatively easy method to assess central noradrenergic activity.

Simultaneous quantitation of catecholamines and metabolites in urine

A semi-automated fluorimetric method for the quantitation of urinary catecholamines (dopamine, noradrenaline and adrenaline) combined with manual methods for the quantitation of their metabolites (homovanillic acid, normetanephrine, metanephrine and vanillylmandelic acid) is described. It provides a sensitive and reproducible analytical technique for routine use. Values obtained in healthy adults are given.