Comparative physiological disposition of N-(phosphonacetyl)-L-aspartate in several animal species after intravenous and oral administration.

The physiological disposition of N-(phosphonacetyl)-L-aspartate (NSC 224131; PALA), a potent inhibitor of aspartate transcarbamylase, has been studied in mouse, rat, dog, and monkey after administration of [14C]PALA at 120 mg/sq m i.v. or p.o. Concentrations of PALA equivalents in plasma, urine, and feces were determined radiochemically, and urine was analyzed chromatographically for PALA. The disposition of PALA equivalents in mouse tissues was determined radioautographically. After i.v. administration, PALA was rapidly (half-time, approximately 1 hr) and extensively (up to 80% of the dose) excreted in the urine of all species. Less than 5% was excreted in the feces. Only PALA was found in the urine of all four species, indicating that the metabolism of PALA, if it occurs at all, is insignificant. PALA equivalents were poorly taken up by mouse tumors and tissues, except kidney, bone, and to a lesser extent, skin and lung, and were rapidly and extensively cleared from all except bone. No differences were apparent in the uptake of PALA equivalents by Lewis lung carcinoma (sensitive to PALA treatment) and L1210 lymphocytic leukemia (insensitive). The pharmacokinetics of PALA in the plasma of rat, dog, and monkey, as well as mouse, were inconsistent with deposition of PALA in tissues and more consistent with the probable distribution of PALA into extracellular water. PALA equivalents were eliminate from all species at a rate (half-time, 1 to 1.5 hr) reflecting the rate of urinary excretion of the drug and at a secondary slower rate probably reflecting the rate of release of bound PALA from sites such as aspartate transcarbamylase. PALA was poorly absorbed into the systemic circulation when administered p.o., in that mouse, rat, and monkey excreted less than 5% of the dose in the urine after p.o. administration. These data on the physiological disposition of PALA explain why high doses of the drug have to be administered to achieve therapeutic and toxic effects, despite the inhibitory potency of the drug on aspartate transcarbamylase. They indicate that PALA will be ineffective administered p.o. and might be contraindicated in patients with impaired renal function and that the kinetics of aspartate transcarbamylase-bound drug is probably more important in determining dose scheduling than the kinetics of free PALA.

The effect of coffee consumption on plasma lipids, lipoproteins, and the development of aortic atherosclerosis in rhesus monkeys fed an atherogenic diet.

Rhesus monkeys (seven females and six males) were fed ad libitum a diet comparable to that consumed by humans, containing 25% by weight fat (40% of calories) and 0.15% cholesterol (0.3 mg/kcal) for 12 months (phase 1). From the 13th month all monkeys were continued on the diet while four females and three males were given 50% coffee as their fluid intake and the remainder were water controls (phase 2). Major changes in total plasma lipids and lipoprotein profiles occurred within 3 months and generally plateaued thereafter. Total plasma protein remained constant while total plasma cholesterol, phospholipids, triglycerides, and free fatty acid levels increased. After the initiation of coffee, there was no difference between the diet-water group and the diet-coffee group with respect to total protein and lipids in plasma. Total concentrations of plasma lipoproteins varied throughout the study. The pre-beta (very low density lipoproteins) fraction remained constant while the beta (low density lipoprotein) and alpha (high density lipoprotein) fractions, along with their major components, increased within 3 to 6 months, then fluctuated in absolute weight thereafter. The introduction of 50% coffee was without effect on the dynamic changes in these fractions as fluctuations were found in both groups and to the same magnitude. This leads the authors to suspect that such variations are "normal" or are in response to the diet per se. The atherogenic diet induced fatty streaks in the aortas of all monkeys to a greater extent in males than females. However, there were no gross differences in the quantity or distribution of the streaks between control and coffee-drinking monkeys.

Hydrolysis of conjugated bile acids by cell-free extracts from aerobic bacteria.

By means of an aerobic enrichment culture technique, several bacteria that hydrolyze conjugated bile acids and modify the formed deconjugates were isolated from feces of man, rat, and chicken and from soil. Hydrolase activity was intracellular and extractable, and the yield of the enzymes was increased by adding the conjugated bile acids to the culture media. The hydrolase from bacterium of human origin was stable, having a pH optimum at about 7.0. All bile acid conjugates were hydrolyzed linearly as a function of time.

Human disposition and some biochemical aspects of methylxanthines.

The human disposition of caffeine, theophylline, and theobromine is essentially characterized by rapid and complete gastrointestinal absorption; minimal first pass metabolism; distribution throughout the total body water; extensive and, in the case of caffeine almost complete, biotransformation in the liver; and elimination of metabolites from the body via the kidneys. Methylxanthine metabolism is affected by such factors as diet, smoking, pregnancy, use of oral contraceptives, age, and disease state. These factors have been studied extensively in relationship to caffeine disposition, less so for theophylline, and minimally for theobromine as well as the metabolites of these compounds, in particular paraxanthine and the diaminouracils. The facts that the loss of the 3-methyl group from caffeine to form 1,7-dimethylxanthine (paraxanthine) is the preferential path of metabolism in humans and that an acetylated diaminouracil is one of the major end-products of caffeine metabolism would indicate the need for additional studies of these compounds. The variability often associated with caffeine disposition may be in part genetic in origin since the population is generally biomodally distributed in its ability to acetylate molecules possessing an amino functional group. In addition, caffeine metabolism may be useful as a diagnostic tool to determine an individual's ability to acetylate and thus eliminate potentially harmful compounds from the body, as well as a measure of liver function in terms of enzymatic metabolizing ability.

Binding of the Cain quinolinium, NSC 113089, to rat tissue lipid extracts.

The binding characteristics of the cancer chemotherapeutic Cain's quinolinium 6-amino-1-ethyl-4-[p-[[p-[(1-ethylpyridinium-4-yl) amino] phenyl] carbamoyl]-anilino]-quinolinium dibromide (NSC 113089) to lipid extracts from rat kidney, liver, heart and skeletal muscle has been studied. Such binding is saturable with an apparent KD congruent to 1.6 microM. Drug binding to the lipid extracts is displaceable by spermine, spermidine, calcium ions and protons. Spermine is the best displacing agent, achieving half drug displacement from the lipid extracts at approximately 6.3 microM regardless of tissue. The inability of the displacing agents to displace all the NSC 113089 bound to the lipid extracts as well as differences in the amount of agent bound to as compared to amount of drug displaced from the lipid extracts indicate that a number of drug binding sites may be present in the lipid extracts. The similarities of drug binding by rat tissue lipids to similar lipids extracted from normal animal and tumor tissues is discussed.

Metabolism of daunomycin (NSC-82151) in vitro and the chemotherapeutic activity of isolated metabolites in vivo.

Daunomycin (D1) was quantitatively converted to a metabolite, D2 (> 98% conversion), by an aerobic, cell-free system containing nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) and the 100,000 x g supernatant fluid of rat kidneys. Under lowered oxygen concentrations, cell homogenates plus NADPH converted D, quantitatively to an unknown metabolite, D(x), with D2 as a possible intermediate. The chromatographic properties of D(x) differed from those of D2 and the aglycones of D1 and D2 (D4 and D3 respectively). Sufficient quantities of D2 and D(x) were prepared using NADPH-supplemented cell-free preparations from the kidneys of rats to assay their chemotherapeutic activity in vivo. The metabolite D2 was as effective as daunomycin (D1) against P388 leukemic cells growing in mice, but only one sixth as active against L1210 leukemic cells growing in suspension culture. The metabolite D(x) was much less active than either D2 or D1 when assayed against L1210 cells growing in culture and was inactive against P388 cells growing in mice.

Purification and characterization of phthalanilide--lipid complexes from tissues.

What appears to be a new class of phospholipids has been isolated from dog brain in the form of complexes with a substituted phthalanilide. The complexes were extracted by chloroform-methanol and purified by countercurrent distribution in solvent systems containing water, chloroform, methanol, and Freon 113. The binding of the phthalanilide congener to lipids has some ionic character. Cations such as H(+) or Ca(++) displaced the phthalanilide from its lipid complex. The pH for 50% displacement acid was about 3.8 and was independent of the purity of the complex. Thin-layer chromatography of the lipid yielded four subfractions of lipid, three of which were ninhydrin-positive and all of which yielded a group of unidentified ninhydrin-positive components on hydrolysis. Each lipid subfraction contained nitrogen, phosphorus, fatty acids, and glycerol but in different ratios. Of the known phospholipids containing nitrogen, none matches the composition and behavior of the lipids isolated as phthalanilide complexes. We have therefore concluded that the phthalanilides bind to a new class of phospholipids characterized by a high content of unidentified ninhydrin-positive components.

Pharmacokinetic considerations in evaluating the effects of tetrahydrouridine on 5-azacytidine chemotherapy in L1210 leukemic mice.

The pharmacokinetics of 5-azacytidine (5-azaCR) and tetrahydrouridine (THU) were considered in evaluating the effect of THU on chemotherapy with 5-azaCR in L1210 leukemia mice. The administration of three different dose levels of THU and 5-azaCR ip in either a 6- or 72-hour infusion gave minimal increases in therapeutic effect. At the high-dose combinations (except in the 72-hour infusion), THU appeared to enhance toxicity. Toxicity, however, occurred only after exceeding a theoretic plasma concentration for 5-azaCR of 61 microgram/ml. THU was effective in increasing the excretion of 5-azaCR by sixfold and in altering its urinary metabolites when given simultaneously with or up to 1 hour prior to 5-azaCR.