Metabolites In Rat Serum Research Articles

High-performance liquid chromatography methods for the separation and quantitation of spironolactone and its degradation products in aqueous formulations and of its metabolites in rat serum

HPLC assays have been developed for the determination of spironolactone and its degradation products 7α-thiospirolactone and canrenone in aqueous solutions of β-cyclodextrins and for the determination of spironolactone and its metabolites 7α-thiospirolactone, 7α-thiomethylspirolactone, 6β-hydroxy-7α-thiomethylspirolactone and canrenone in rat serum samples. Both methods were well suited for their respective applications, i.e., studying the stability of spironolactone in liquid formulations of β-cyclodextrins and the oral absorption of spironolactone in rats. The HPLC method developed for spironolactone and its metabolites in rat serum requires very small volumes of serum making it possible to take several blood samples over a period of time.

Selective inhibition of isoprenylation of 21-26-kDa proteins by the anticarcinogen d-limonene and its metabolites.

Limonene has chemotherapeutic activity against chemically induced rat mammary carcinomas, many of which contain activated ras genes. Given the recent discovery of the post-translational modification of p21ras and other cell growth-associated proteins by intermediates in the mevalonic acid pathway, and the common biochemical origins of limonene and these isoprene products, we investigated the effect of limonene on protein isoprenylation. NIH3T3 and human mammary epithelial cells were incubated with lovastatin and [2-14C]mevalonolactone in the absence and presence of limonene. Labeled proteins were then subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Limonene inhibited isoprenylation of a class of cellular proteins of 21-26 kDa, including p21ras and possibly other small GTP-binding proteins, in a dose-dependent manner in both cell lines. In contrast, limonene did not affect the isoprenylation of several other proteins, including nuclear lamins. Limonene is metabolized extensively in vivo but not in cultured cells. The two major rat serum metabolites of limonene, perillic acid and dihydroperillic acid, were more potent than limonene in the inhibition of isoprenylation. These results demonstrate that limonene selectively inhibits isoprenylation of 21-26-kDa proteins at a point in the mevalonic acid pathway distal to 3-hydroxy-3-methylglutaryl coenzyme A reductase, and they provide a plausible explanation for its chemotherapeutic activity. Inhibition of isoprenylation of proteins such as p21ras and other small GTP-binding proteins would alter their intracellular localization and, hence, disrupt their biological activity.

High-performance liquid chromatographic determination of propranolol and its metabolites in rat serum

High-performance liquid chromatographic determination of propranolol and its metabolites in rat serum

Chromatographic and cytogenetic analysis of in vivo metabolites of fluoranthene

Fluoranthene metabolites in rat serum were analysed by high-performance liquid chromatography (HPLC) with UV and fluorescence detection and compared with in vitro metabolites obtained by incubation with microsomal fraction of rat hepatocytes. In order to resolve very polar fluorescent compounds present in rat serum, a modification of HPLC existing methods for in vitro metabolites separation was necessary. Mutagenic 2,3-dihydrodiol was identified in both in vitro sample and rat serum: this result is in good accord with cytogenetic analysis on rats bone marrow cells, that shows a slight but significant increase of sister chromatide exchanges.

Simultaneous determination of diazepam and its active metabolites in rat serum, brain and cerebrospinal fluid by high-performance liquid chromatography

Simultaneous determination of diazepam and its active metabolites in rat serum, brain and cerebrospinal fluid by high-performance liquid chromatography

The distribution of (5E)-(10S)-10, 19-dihydroercalciol and its metabolites in serum of rats

The distribution of radioactivity in serum of male rats (275 g) after oral administration of tritium labelled (5E)-(10S)-10, 19-dihydroercalciol (dihydrotachysterol 2) has been studied as a function of time and dose level. Nine distinct radioactive substances, chromatographing in the range between calciol and calcitriol, could be demonstrated. No attempt was made to establish chemical structures. After a single dose of 1.84 nmol, (5E)-(10S)-10, 19-dihydroercalciol is very rapidly metabolized to more polar forms. The time course of appearance, ranging between 30 min and 1 day after administration, and the polarity of these substances indicated that they might be formed in sequence. The highest serum concentrations of the major substances occurred between 2 h and 10 h after administration, but compared with the dosage they were very low. In response to daily administration the concentrations of the major substances achieved steady-state levels within 1–4 days. The metabolism of (5E)-(10S)-10, 19-dihydroercalciol was apparently not affected by its nutritional status at the dose level studied. After single administration of progressively increasing doses, ranging from 1.84 nmol to 1.84μmol, the relative increments of the concentrations of the major substances rose in proportion to the relative increases of the dosage. The mechanisms responsible for the appearance of these substances in serum were found to be closely related. At dose levels up to 18.4 nmol feedback control was apparently absent.