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M Kumlin

Publications and source records attributed to M Kumlin.

62 records · Page 4Linked to original sources
PubMed1986

Identification of 11-dehydro-TXB2 as a suitable parameter for monitoring thromboxane production in the human.

In order to identify suitable parameters for measurement of thromboxane production in vivo, the metabolism of TXB2 was studied in the human. [3H8]-TXB2 was given intravenously to a healthy human volunteer. Blood samples were collected for 50 min after the injection, and urine was collected for 24 hours. The urinary and blood metabolic profiles were visualized by the use of two-dimensional TLC and autoradiography. Identification of metabolites was achieved with GC/MS and in some cases by cochromatography with reference compounds in TLC and GC. In blood, unmetabolized TXB2 was the dominating compound during the first 30 min. Three less polar metabolites appeared, two of which were identified as 11-dehydro-TXB2 and 11,15-didehydro-13,14-dihydro-TXB2, respectively. The third compound was tentatively identified as 15-dehydro-13,14-dihydro-TXB2. Since 11-dehydro-TXB2 was one of the major metabolites in blood as well as urine, it was deemed suitable as target for measurement of thromboxane production in vivo. The advantages of 11-dehydro-TXB2 over its parent compound, TXB2, were demonstrated in experiments where unlabeled TXB2 was injected i.v. to a human volunteer, and the blood and urinary levels of both compounds were then followed by radioimmunoassay. Measured levels of 11-dehydro-TXB2 were found to give a more reliable picture of metabolic events than TXB2, the latter compound to a large extent reflecting technical difficulties during blood sample collection.

Autoradiography↗
PubMed1986

Circulating and urinary thromboxane B2 metabolites in the rabbit: 11-dehydro-thromboxane B2 as parameter of thromboxane production.

The metabolism of thromboxane B2 was studied in the rabbit. The aim of the study was to identify metabolites in blood and urine that might serve as parameters for monitoring thromboxane production in vivo. [5,6,8,9,11,12,14,15-3H8]-Thromboxane B2 was administered by i.v. injection to rabbits, and blood samples and urine were collected with brief intervals. The metabolic profiles were visualized by two-dimensional thin layer chromatography and autoradiography, and the structures of five major metabolites were determined using chromatographic and mass spectrometric methods. In urine the major metabolites were identified as 11-dehydro-TXB2 and 2,3,4,5-tetranor-TXB1, and other prominent products were 11-dehydro-2,3,4,5-tetranor-TXB1, 2,3-dinor-TXB1 and 2,3-dinor-TXB2. In the circulation, TXB2 was found to disappear rapidly. The first major metabolite to appear was 11-dehydro-TXB2, which also remained a prominent product in blood for the remainder of the experiment (90 min). With time, the profile of circulating products became closely similar to that in urine. TXB2 was not converted into 11-dehydro-TXB2 by blood cells or plasma. The dehydrogenase catalyzing its formation was tissue bound and was found to have a widespread occurrence: the highest conversion was found in lung, kidney, stomach and liver. The results of the present study suggest that 11-dehydro-TXB2 may be a suitable parameter for monitoring thromboxane production in vivo in the rabbit in blood as well as urinary samples, and possibly also several tissues. This was also demonstrated in comparative studies using radioimmunoassays for TXB2 and 11-dehydro-TXB2.

Alcohol Oxidoreductases↗
PubMed1986

Radioimmunoassay for 11-dehydro-TXB2: a method for monitoring thromboxane production in vivo.

A radioimmunoassay was developed for 11-dehydro-TXB2, a prominent metabolite of TXB2 in blood and urine of several species. In order to reliably assay 11-dehydro-TXB2, its chemical stability as well as its chromatographic properties were first examined. Since dehydrogenation at C-11 converts the thromboxane ring into the delta-lactone form of a dicarboxylic acid, which can also occur in an open form, the analysis of 11-dehydro-TXB2 may be somewhat complicated. In some chromatographic systems, the compound thus migrated with pronounced tailing, and during extraction using the common Sep-Pak procedure the two forms were partially separated. The lactone as well as the open form could be conclusively identified using mass spectrometry. The equilibrium between the two forms of 11-dehydro-TXB2 was studied in buffers of different pH and in plasma. Higher pH favoured hydrolysis into the acyclic structure. The lactonization and hydrolysis processes were also shown to be time and temperature dependent. Two different antiplasms, raised in rabbits against conjugates of 11-dehydro-TXB2 with bovine serum albumin, displayed somewhat different properties in their recognition of the two forms of 11-dehydro-TXB2. A radioimmunoassay employing these antibodies was developed. The labeled antigen was prepared by incubation of 3H-TXB2 with rabbit lung supernatant. The limit of detection was 1.5 pg. For validation of the assay, analysis of blood and urinary samples, obtained after injection of TXB2 to a human volunteer, was done. The values obtained were compatible with previous isotope studies. Results from an inhibition experiment with rabbit lung incubated in the presence or absence of indomethacin further supported the identity of the assayed substance.

Animals↗
PubMed1986

Leukotrienes and other eicosanoids as mediators of airway obstruction.

Prostaglandins and related compounds comprise an ubiquitous biological system which utilizes arachidonic acid (5,8,11,14-eicosatetraenoic acid) as a common cellular precursor to synthesize a great number of substances with a broad range of activities, including participation in the cellular and humoral events of inflammation and allergy. Briefly, prostaglandins and thromboxanes (TX) are formed in reactions initiated by the aspirin-sensitive fatty acid cyclooxygenase, whereas leukotrienes (LT) and several other compounds are generated by different lipoxygenases present in human tissues. In the field of asthma, the mast cell-derived PGD2 alpha, as well as PGF2 alpha and TXA2 are known as reasonably potent bronchoconstrictors, and asthmatics are remarkably hyperreactive to inhalation of PGF2 alpha. However, the therapeutic failure of aspirin and related cyclooxygenase inhibitors in the treatment of asthma suggests that these compounds are less likely to be primary mediators. On the other hand, several lines of evidence indicate that three closely related leukotrienes, LTC4, LTD4 and LTE4, previously known as slow-reacting substance of anaphylaxis (SRS-A), have the potential to be major mediators of the airway perturbations characteristic of bronchial asthma. Thus, as documented both in experimental animals and in man, these leukotrienes are exquisitely potent in causing bronchial smooth muscle contraction, mucosal edema, and secretion of mucus into the lumen. In particular, LTC4, LTD4 and LTE4 have been linked to allergic asthma because allergen challenge is a potent stimulus for their release from, e.g., lung tissue of asthmatics. In fact, it has been documented that inhibition of leukotriene formation can block allergen-induced contractions of isolated human bronchi.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Use of tritium labeled amino acid conjugates of prostaglandins and thromboxanes as labeled ligands in prostanoid radioimmunoassay.

Conjugates of prostaglandins and thromboxanes with tritium labeled amino acids were prepared and employed as labeled ligands in prostaglandin and thromboxane radioimmunoassays. Assays for PGF2 alpha, 15-keto-13, 14-dihydro-PGF2 alpha, TXB2 and 15-keto-13,14-dihydro-TXB2 were evaluated in comparative studies using either these heterologous ligands or the corresponding homologous tritiated eicosanoid as tracers. Binding properties for the respective antibodies were found to be similar using either tracer. Three biological studies were also conducted, viz. study of the release of TXB2 during collagen induced platelet aggregation, of 15-keto-13,14-dihydro-TXB2 during guinea pig pulmonary anaphylaxis, and of PGF2 alpha (measured as 15-keto-13,14-dihydro-PGF2 alpha in peripheral plasma) during bovine luteolysis. The analyses gave comparable results using either the heterologous or the homologous assay. Thus, this type of labeled prostanoid conjugates may serve as a convenient alternative to homologous tracers in radioimmunoassay. Heterologous tracers may even in certain cases provide the only simple solution to the problem of preparing a labeled ligand of high specific activity.

Amino Acids↗