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K M Straub

Publications and source records attributed to K M Straub.

29 records · Page 2Linked to original sources
PubMed1977

Identification of the major adducts formed by reaction of benzo(a)pyrene diol epoxide with DNA in vitro.

Covalent binding of the benzo[a]pyrene metabolite (+/-)7beta,8alpha-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene to calf thymus DNA was investigated. Enzymatic hydrolysis of the carcinogen-modified DNA and subsequent separation via reversed-phase high-pressure liquid chromatography resulted in the detection and isolation of seven distinct products. High-resolution mass spectrometry indicates that these products are covalent adducts of deoxyguanosine, deoxyadenosine, and deoxycytidine. The deoxyguanosine and deoxyadenosine adducts involve binding between the activated hydrocarbon (benzo[a]pyrene diol epoxide) and exocyclic amino groups of the respective purines.

Adenine↗
PubMedDate not supplied

Characterization of hapten binding to immunoconjugates by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) has been used to characterize the covalent binding of different haptens to the enzyme glucose 6-phosphate dehydrogenase. The technique allows one to directly observe the relative amounts of each conjugated species present in a mixture, as well as the average hapten number. These measurements are useful for optimizing reaction conditions to yield a more precisely defined product for use in immunoassays. The results obtained show that ESI-MS with a quadrupole analyzer can be successfully used to analyze mixtures of derivatized proteins in the molecular weight range of 50-60 kDa, where the modifying hapten has a molecular weight as low as 130 Da.

Binding Sites↗
PubMedDate not supplied

Metabolism of the leukotriene receptor antagonist 5-(2-(8-phenyloctyl)phenyl)-4,6-dithianonanedioic acid (SK&F 102922) in the guinea pig. Rearrangement of the acyl glucuronide.

A primary route of inactivation of leukotrienes and their receptor antagonists (LTRA) is metabolism by omega oxidation. SK&F 102922 [5-(2-(8-phenyloctyl)phenyl)-4,6-dithianonanedioic acid] is a LTRA that was designed to be resistant to omega oxidation. Therefore, these experiments were designed to characterize the metabolic fate of [14C]SK&F 102922. Following iv administration of SK&F 102922 (5 mg/kg), 80% of injected radioactivity was excreted in bile in 1 hr. At least five metabolites and parent (18% of administered dose) were present in bile. One metabolite (M1), which accounted for less than 10% of the excreted radioactivity, was monohydroxylated. Three metabolites (M2, M3A, and M3B), which together accounted for greater than 50% of excreted radioactivity, had mass spectra consistent with acyl glucuronides. All three metabolites were alkali labile, whereas only one metabolite (M2) was susceptible to beta-glucuronidase hydrolysis. These data indicate that M3a and M3b are nonglycosidic isomers of M2 that were formed by a nonenzymic reaction involving migration of the aglycone (SK&F 102922) from C-1 to C-2, C-3, or C-4 of glucuronic acid. The 1-O-acyl-beta-glucuronide of SK&F 102922 (M2) exhibits pH dependent rearrangement, with half-lives ranging from 1 to greater than 1000 hr. Therefore, acyl glucuronidation can account for much of the metabolic fate of SK&F 102922 and, potentially, other structurally related LTRAs or endogenous leukotrienes themselves.

Animals↗
PubMedDate not supplied

In vitro microsomal metabolism of the leukotriene receptor antagonist, 5-(2-dodecylphenyl)-4,6-dithianonanedioic acid (SK&F 102,081).

In vivo experiments indicate that the major route of metabolism of SK&F 102,081 [5-(2-dodecylphenyl)-4,6-dithianonanedioic acid] is via omega-oxidation and subsequent beta-oxidation. Therefore, in vitro experiments were designed to characterize the initial reaction of this pathway, omega-hydroxylation. SK&F 102,081 was metabolized by rat hepatic microsomes to two products; mass spectral analysis indicated that these products were the omega (omega) and omega minus one (omega-1) hydroxylated metabolites, 5-[2-(12-hydroxy)dodecylphenyl]-4,6-dithianonanedioic acid and 5-[2-(11-hydroxy)dodecylphenyl]-4,6-dithianonanedioic acid, respectively. NADPH and oxygen were required for the formation of these metabolites. Kinetic analysis of omega- and (omega-1)-hydroxylations of SK&F 102,081 indicated that the apparent Km for (omega-1)-hydroxylation (52.6 microM) was approximately 2.5-fold higher than the apparent Km for omega-hydroxylation (22.0 microM). Furthermore, the cytochrome P-450 inhibitor, metyrapone, produced differential inhibition of omega- and (omega-1)-hydroxylation. In addition, the terminal acetylenic analogue of SK&F 102,081, SK&F 103,600 (5-[2-(11-dodecynyl)phenyl]-4,6-dithianonanedioic acid), produced differential suicide inactivation of SK&F 102,081 omega- and (omega-1)-hydroxylations. These studies indicate that the omega- and (omega-1)-hydroxylations of SK&F 102,081 are probably carried out by different isozymes of hepatic cytochrome P-450 in the rat. Furthermore, the isozymes that hydroxylate SK&F 102,081 at the omega- and (omega-1)-positions may be similar to those which mediate similar reactions on endogenous compounds such as prostaglandins and leukotrienes.

Animals↗
PubMedDate not supplied

In vivo metabolism of the leukotriene receptor antagonist, 5-(2-dodecylphenyl)-4,6-dithianonanedioic acid (SK&F 102,081) in the guinea pig.

Both leukotrienes and their receptor antagonists possess substantial pharmacologic activity in in vitro systems, but their duration of action in vivo is extremely short. The exact mechanism of rapid inactivation of these lipids is unknown, but is likely due to metabolism. Therefore, the metabolic fate of a model antagonist 5-(2-dodecylphenyl)-4,6-dithianonanedioic acid (SK&F 102,081) was elucidated in anesthetized guinea pigs. Following iv administration of [14C]SK&F 102,081 (5 mg/kg), 85% of injected radioactivity was excreted in bile in 1 hr. Approximately 6% of the radioactivity in bile was associated with parent. At least 14 metabolites were present in bile, 2 of which accounted for almost 60% of the excreted radioactivity. Identification of biliary metabolites revealed that metabolism occurred by two major routes, omega-oxidation with subsequent beta-oxidation and acyl glucuronidation at approximately a 4:1 ratio. Since current structure-activity relationships suggest that omega-oxidation results in the loss of pharmacologic activity of SK&F 102,081, the rapid loss in pharmacologic activity observed in vivo may be due to rapid metabolism.

Animals↗