Svante B. Ross

Erythrocyte catechol‐O‐methyltransferase activity in a Swedish population

Erythrocyte catechol‐O‐methyltransferase (COMT) activity has been analyzed in 185 individuals. The activities showed a trimodal frequency distribution. This suggests an autosomal codominant inheritance of the human erythrocyte COMT activity. The mean male COMT activity was 18.9 ± 7.0 (S.D.) nmol/ml RBC/h. The mean female activity was 16.1 ± 6.3 nmol/ml RBC/h and the frequency distribution pattern for women was shifted towards lower values.

Regional in vivo binding of [3H]N-propylnorapomorphine in the mouse brain. Evidence for labelling of central dopamine receptors

Tail vein injections of [3H]N-propylnorapomorphine ([3H]NPA) in male mice resulted in a dose-related accumulaton of radioactivity in the following brain regions: striatum (max), olfactory tubercle and cerebellum (min). The specific binding was saturable with increasing concentrations of the drug and stereospecifically displaced by (+) butaclamol. Dopamine agonist (apomorphine, NPA and bromocriptine) and antagonists (spiperone, haloperidol, (+) butaclamol and I-sulpiride) all caused dose-dependent prevention of [3H]NPA binding. Mianserin, phenoxybenzamine and propranolol did not prevent the in vivo [3H]NPA binding suggesting that [3H]NPA binds specifically to dopamine receptors in the striatum and the olfactory tubercle of the mouse.

Concentration and Uptake of 5-Hydroxytryptamine in Platelets from Cluster Headache and Migraine Patients

Concentrations of 5-hydroxytryptamine (5-HT) in platelets were determined in 33 cluster headache patients (17 males) and in 34 migraine patients (16 males) outside attacks. The 5-HT uptake into platelets was measured and the kinetic constants Vmax and Km determined in 26 cluster patients (14 males) and in 30 migraine patients (13 males). Significantly lower 5-HT concentrations in whole blood were found in cluster headache and migraine patients than in 50 healthy controls (19 males). The Vmax and Km values of the 5-HT uptake were significantly lower in cluster headache and migraine patients compared with 22 healthy controls (9 males). The 5-HT concentrations and the kinetics of the 5-HT uptake did not differ between cluster headache and migraine. In healthy controls a significant positive correlation was found between the 5-HT uptake rate at 0.25 μM and Km but not in cluster headache and migraine patients. The 5-HT concentrations in whole blood correlated positively with Vmax and Km, respectively, in cluster headache and with Km in healthy controls but not with Vmax nor with Km in migraine. There was no obvious relation between the kinetics of platelet monoamine oxidase (MAO) and the 5-HT uptake except for an increased incidence of low Vmax of MAO and low Km of the 5-HT uptake in cluster headache. The kinetics of the 5-HT uptake was apparently not related to the state of migraine. The results indicate a possible constitutional trait in cluster headache and migraine expressed as low 5-HT concentrations in whole blood and low Vmax and Km of the 5-HT uptake into platelets.

Pharmacological and toxicological exploitation of amine transporters

Abstract In these sophisticated days of advanced receptorology, a general view holds that factors such as uptake mechanisms have little interest for pharmacologists and toxicologists. But Svante Ross presents a new perspective. The re-uptake mechanisms in the membranes of the monoaminergic neurones, the amine transporters, are not specific for the transmitter amines but also transport compounds structurally related to the natural substrates. This makes the amine transporters suitable as specifically targeted delivery systems for drugs. On the other hand, such transporting systems also make these neurones vulnerable to toxic effects of compounds as a result of their neuronal accumulation.

Monoamine oxidase in human platelets: Kinetics and methodological aspects

Abstract The kinetic properties of human platelet monoamine oxidase (MAO) were examined in 20 apparently healthy controls. The mean value (±S.D.) of the maximum velocity ( V ) was found to be 5.36 ± 1.97 pmoles of product formed/10° platelets/min and the Michaelis-Menten constants were for phenethylamine ( K PEA m ) 14.6 ± 8.20 μ M and for oxygen ( K m O 2 )254 ± 125 μ M, when assayed in 0.1 M phosphate buffer, pH 7.4. The relation between the value of the corresponding apparent constants was studied. Inhibition of the enzyme activity was seen at 20 μM of PEA and 180 μM of oxygen. The enzyme kinetics were also studied at different pH. Two p K values were found, p K 1 = 6.65 and p K 2 = 6.95. The influence of homogenization on the MAO activity was compared with the activity in the undisrupted platelet. At PEA concentrations below 10 μM higher MAO activities were found in the intact cell. A 15 per cent loss of activity was detected in platelet samples after storing at −20° for three and a half years.

Platelet monoamine oxidase in a pedigree with schizophrenia: an interlaboratory project.

Conflicting reports on the association between platelet MAO activity and schizophrenia prompted a critical review and determinations on identical samples at one laboratory in Sweden and one in the USA. Samples originated from eight schizophrenics and 27 relatives belonging to a large pedigree, thus ensuring biological homogeneity.

Catechol-O-Methyltransferase Activity in Human Erythrocytes: Methodological Aspects

Different methodological aspects on the assay of human erythrocyte catechol-O-methyltransferase (COMT) activity were studied. No temporal variations were found either over a 24 hour period or over one month. Erythrocytes from whole blood collected with any of the anticoagulants heparin, EDTA or citrate could be used as the enzyme source provided the cells were washed in saline. The COMT activity in lysed erythrocytes was rapidly lost when the lysate was stored at +4 degrees C and -20 degrees C. Intact erythrocytes could be stored up to one week in +4 degrees C without considerable loss of activity. The COMT activity was stable for at least two years when storing the cells at -85 degrees C. Freeze-thawing and hypotonic disruption of the erythrocytes resulted in the same activity and neither freeze-thawing nor sonication altered the apparent Km for the substrate. Noradrenaline and 3,4-dihydroxybenozic acid (DBA) could both be used as substrates although DBA gave higher activity values and had a higher affinity to the enzyme. The COMT activity increased with increasing concentration of the methyl-donor S-adenosyl-1-methionine up to approximately 0.1 mM. Preincubation at 47 degrees C decreased the COMT activity whereas the apparent Km values remained unchanged. The present COMT assay was convenient and reproducible and could be used with small amounts of blood with different kinds of anticoagulants. Interactions with plasma factors were avoided by washing the erythrocytes with isotonic sodium chloride.

Kinetic aspects of monoamine oxidase activity in twins with psychoses

Monoamine oxidase activity was assayed in platelets from 22 (8 monozygotic and 14 dizygotic) twin pairs. At least one twin of each pair had a serious psychiatric disorder (proband). Phenethylamine was used as substrate and the assay was performed at two different oxygen concentrations (0.06 and 0.12 mM). Apparent Km and Vmax values were estimated from double reciprocal plots. The correlation between proband and control twins was high for both apparent Km (r=0.83) and Vmax (r = 0.69) when the enzyme was assayed at the higher concentration of oxygen. The monozygotic twins pairs showed very high correlations (Km r=0.93; Vmax, r = 0.86)as compared to dizygotic twins (Km r = 0.81, Vmax r = 0.50) and apparently healthy subjects (Km r = 0.46, Vmax r = 0.33). No difference in kinetic properties was found between schizophrenic and non‐schizophrenic twins.