Tracazolate metabolites in rat tissue.

Tracazolate (4-n-butylamino-1-ethyl-6-methyl-1H-pyrazolo[3,4-b] pyridine-5-carboxylic acid ethyl ester) undergoes extensive biotransformation to lipophilic metabolites following oral dosage to male rats. Twenty-one metabolites were identified in a plasma hexane extract by mass spectrometry. Coadministration of unlabeled tracazolate with its stable carbon-13 isotope expedited the isolation and identification of 11 biotransformation products. The various metabolites resulted from either hydrolysis, oxidation, dealkylation, or conversion of an ethyl group to a vinyl group and also from combinations of these biotransformation reactions. Brain extract contained tracazolate and 12 of the metabolites found in plasma. Extracts of fat contained tracazolate and nine of the plasma metabolites. An uncommon type of metabolite less polar than tracazolate (1-vinyl tracazolate) was isolated by HPLC and identified by mass spectrometry.

Metabolism, disposition, and pharmacokinetics of tracazolate in rat and dog.

The metabolism, disposition, and pharmacokinetics of tracazolate, (4-butylamino-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester), a novel anxiolytic agent, were studied in rat and dog following single oral and iv doses. Although tracazolate exhibits very good absorption (greater than 80%) in both species, it is extensively metabolized, accounting for low bioavailability. Excretion of 14C was rapid, with the kidney being the major organ of excretion. Tracazolate was not detected in the urine after iv doses even though measurable levels were found in blood, suggesting reabsorption of the compound by the renal tubules. The logarithm of the blood drug concentration vs. time data for both species was best described by a three-compartment open model. Mean t1/2 (beta) for tracazolate in the rat and dog were 14 and 10 hr, respectively. The distribution of radioactivity in rats showed that the concentrations of 14C and 14C-tracazolate were greater in tissues than in blood. Tracazolate was the predominant radioactive compound in brain during the first 6 hr and in fat for 96 hr. The extent and decay of tracazolate in fat strongly suggest that this tissue contributes significantly towards the equilibrium of drug between "deep body compartments" and blood. The major metabolite in blood was de-esterified tracazolate (ICI-US 7773) and in brain the gamma-ketotracazolate (ICI-US 10052).

Determination of ethinyl estradiol in human urine by radiochemical GLC.

A radiochemical GLC analysis was developed for 3H-labeled ethinyl estradiol in human urine. The technique was applied to the unconjugated and aglycone fractions of urine collected from women who were dosed orally with: (a) single capsules containing 2.0 mg of 3H-quinestrol (900 muCi) and 2.5 mg of unlabeled quingestanol acetate dissolved in sesame oil and (b) single tablets containing 100 microgram of 3H-quinestrol (86 muCi). Unconjugated ethinyl estradiol in Day 1 urine collections represented means of 0.02% of the high quinestrol dose and 0.12% of the low dose. Ethinyl estradiol glucuronide in the same collections represented means of 0.55% of the high drug dose and 1.35% of the low dose. The method could detect 1-ng quantities of 3H-ethinyl estradiol and 3H-quinestrol.

Radiochemical GLC assay for nortriptyline in human plasma.

A novel method was developed for the assay of nortriptyline in plasma. After nortriptyline was extracted, it was acetylated with 3H-acetic anhydride; the quantity of 3H-acetylnortriptyline in the extract was determined by radiochemical GLC. The method is capable of assaying 5 ng of nortriptyline/ml of plasma. The instrumentation was assembled from commercially available components.

Assay of human plasma for nortriptyline by radioacetylation and thin-layer chromatography.

A highly specific and sensitive thin-layer chromatographic method for determining nortriptyline levels in plasma is presented. The procedure involves extracting nortriptyline, acetylating it with radioactive acetic anhydride, resolving acetylnortriptyline by thin-layer chromatography, and measuring its radioactivity.

Implications of the reorganizational behavior of condensed phosphates for mitochondrial phosphorylation.

The composition of phosphorus-32 labeled polyphosphoric acid (32PPA) prepared from, (i) H3(32)PO4 and (82 percent w/w) P2O5 and, (ii) by incorporation of radioactivity from H3(32)PO4 into unlabeled polyphosphoric acid (PPA) was examined and found to be the same. The identity of these condensed phosphorate mixtures, as established, argues strongly in favor of a rapid and complete equilibration and provides direct evidence in support of Van Wazer's reorganization theory of condensed phosphates. No evidence for metaphosphates or label exchange in an aqueous environment was found. 32PPA was found to exist in metastable equilibrium with 32PPA as a crystalline solid of different composition. Agreement of hydrolytic rate data from the mixtures of condensed phosphates with literature values for individual species suggests that the hydrolysis of the pyro- and tripoly-phosphate species proceeds independently in the presence of other homologs. The rate of hydrolysis of the condensed phosphates (at pH5.0 and 65 degrees C) was found to be proportional to chain length, increasing about four-fold between pyro- and hexapoly-phosphate. The same correlation is also manifest in the adenosine 5' polyphosphates. A slight enhancement in the rate of hydrolysis of adenosine diphosphate, increasingly more pronounced in the case of adenosine tri- and tetra-phosphate, was also noted. This effect is attributed to the presence of the adenosine moiety. The most interesting aspect of the rate data is to be found in the similarity of the rates of hydrolysis of the adenosine 5' polyphosphates, relative to their inorganic polyphosphate counterparts. The significance of these findings is discussed and the viewpoint is presented that the properties of condensed phosphates are compatible with the requisite characteristics that must be predicated of any in situ phosphoryl precursor in mitochondrial phosphorylation.

Quingestanol acetate metabolism in women.

PIP: The metabolism of quingestanol acetate (QA) was studied in 3 women, and an assessment of the bioavailability of the oral dosage form was made. QA was absorbed rapidly and showed a high order of bioavailability after oral administration. The composition of the radioactive steroids in the plasma suggests that the initial biotransformation of the drug involves 2 pathways, the deacylation to quingestanol and O-dealkylation to norethindrone acetate, and that both of these metabolites are subsequently converted to norethindrone.^ieng