Biomedical subjects

A Riutta

Publications and source records attributed to A Riutta.

5 recordsLinked to original sources

PubMed1992

Solid-phase extraction of urinary 11-dehydrothromboxane B2 for reliable determination with radioimmunoassay.

In this paper we elaborate a one-step procedure for the selective extraction of urinary 11-dehydrothromboxane B2 on octylsilyl silica cartridges for reliable determination with radioimmunoassay. The immunoreactivity profile of nonselectively extracted urine after HPLC separation showed that as much as 70% of the total 11-dehydrothromboxane B2 immunoreactivity comigrates with polar interfering material. Its amount could be considerably decreased using acetonitrile:water (18:82, v/v) as wash solvent before elution of 11-dehydrothromboxane B2 from the cartridge. Alternatively, very high immunoreactive purity was achieved without the preceding wash step by selective elution of the analyte with dichloromethane:hexane (70:30). After both optimized steps in the extraction procedure were combined, immunoreactivity was found only in HPLC fractions corresponding to the retention volume of authentic 11-dehydrothromboxane B2. The homogeneity of this immunoreactivity was confirmed by two-step HPLC separation. A significant correlation of values was observed between samples measured after extraction and those measured after subsequent HPLC purification. A high correlation was also found with concentrations determined by radioimmunoassay using four different antisera. The values of 24 h excretion of 11-dehydrothromboxane B2 in 10 male volunteers (595 +/- 114 ng/g creatinine, mean +/- SD) as well as the inhibitory effect of acetylsalicylic acid (80 +/- 13%) closely correspond with those reported in the literature. This selective extraction procedure provides a high validity in radioimmunoassay without requiring any further purification step.

Chromatography, High Pressure Liquid↗

PubMed1992

Effects of catecholamines on eicosanoid synthesis with special reference to prostanoid/leukotriene ratio.

Catecholamines (adrenaline, dopamine, and noradrenaline) stimulate prostanoid synthesis by acting as "cosubstrates." On the other hand, many inhibitors of leukotriene synthesis, such as nordihydroguaiaretic acid and caffeic acid, have a catecholic structure. Catecholamines have opposite effects on prostanoid and leukotriene synthesis in human polymorphonuclear leukocytes and whole blood. Basic phenols (catechol, hydroquinone, and phenol) also increase the prostanoid/leukotriene ratio in polymorphonuclear leukocytes. These actions correlate to their antioxidant capacities and oxidation potentials, and they are not mediated via adrenergic receptors. There is only limited knowledge about the effects of natural catecholamines on the prostanoid/leukotriene ratio in vitro and in vivo. Indirect data suggest that catecholamines could increase prostanoid production in physiological or pathological situations, such as heavy physical exercise, myocardial infarction, and surgical stress. This interaction may also be of clinical importance in asthma, gastric ulcer, and psoriasis, where decreased prostanoid/leukotriene ratios have been reported.

Animals↗

PubMed1992

Adrenaline stimulates thromboxane and inhibits leukotriene synthesis in man.

Catecholamines and other catecholic compounds have opposite effects on the cyclooxygenase and 5-lipoxygenase pathways of arachidonic acid metabolism in human polymorphonuclear leukocytes and whole blood in vitro. The hypothesis that high levels of adrenaline, found e.g. in myocardial infarction, are involved in the regulation of arachidonic acid metabolism was tested. Adrenaline (0.1 micrograms/kg per min for 45 min and thereafter 0.2 micrograms/kg per min for 15 min) was infused to healthy male volunteers to mimic relationships between high levels of adrenaline and arachidonic acid metabolism in myocardial infarction. Adrenaline infusion increased Ca ionophore A23187-induced TXB2 formation in whole blood. The effect was smaller when spontaneous clotting was used as a stimulus. Urinary 11-dehydro-TXB2 excretion, an indicator of total in vivo thromboxane synthesis, increased twofold. Adrenaline infusion decreased both LTB4 and LTE4 synthesis in A23187-stimulated whole blood. These results demonstrate that high levels of adrenaline influence the cyclooxygenase and 5-lipoxygenase pathways of arachidonic acid metabolism differentially in man.

Adult↗

PubMed1991

Catecholamines decrease leukotriene B4 and increase thromboxane B2 synthesis in A23187-stimulated human whole blood.

Catecholamines (adrenaline, dopamine, isoprenaline, noradrenaline) and caffeic acid (catecholic compound without adrenergic receptor activity) decreased leukotriene (LT)B4 synthesis in A23187-stimulated human whole blood. Salbutamol, a non-catecholic beta 2-adrenergic agonist, did not influence LTB4 synthesis. Catecholamines stimulated thromboxane (TX)B2 synthesis with a concomitant inhibition of LTB4 synthesis; caffeic acid and salbutamol did not stimulate TXB2 synthesis. These results, obtained in A23187-stimulated whole blood, which also takes into account the complex interaction between different cell types, are similar to our previous results with polymorphonuclear leukocytes. Catecholamines show an opposite effect on lipoxygenase and cyclooxygenase pathways, which may give rise to a marked change in LT/TX ratio in physiological or pathological conditions where sufficient concentrations of catecholamines are present.

Calcimycin↗

PubMed1991

Factors affecting the reliability of direct radioimmunoassay for urinary 11-dehydrothromboxane B2 with 125I-labelled ligand: albumin and heterogeneous immunoreactivity.

The determination of 11-dehydrothromboxane B2 (11-dehydro-TXB2) from unextracted human urine was studied by means of a specific radioimmunoassay based on the use of the 125I-labelled tyrosine methyl ester derivative of 11-dehydro-TXB2 as radioligand. The assay was evaluated in various incubation media by either dextran-coated charcoal (DCC) or polyethylene glycol (PEG) separation. Both the non-specific and the specific binding showed high variation in different assay media with DCC separation but with the use of PEG separation, however, the non-specific binding was constant. The verification tests carried out in both separation systems revealed a high variation of equilibrium with the individual samples. The albumin content of urine is proposed to be one important factor underlying poor reliability of direct radioimmunoassay. Both the immunoreactivity profiles observed after HPLC separation and the apparent 11-dehydro-TXB2-like immunoreactivity values determined by direct radioimmunoassay demonstrated that the unextracted urine contained a high ratio of interfering materials. It is concluded that efficient purification of human urine before determination is essential when this type of 125I-labelled radioligand is employed in radioimmunoassay.

Albumins↗