Plasma kinetics and urinary elimination of saccharin in man

The plasma kinetics and urinary elimination of saccharin were studied in 3 groups each of 5 healthy male volunteers given the sweetener as three different single oral doses (50, 150 and 333 mg/60 kg body weight). Saccharin concentrations were determined by gas liquid chromatography-stable isotope dilution mass fragmentography. The compound was rapidly absorbed through the gastrointestinal tract, reaching plasma peak concentrations between 30 and 60 min after intake. Plasma saccharin elimination was also fast, with a monoexponential pattern of decay. At the 3 doses studied saccharin was excreted in urine within a few hours, about 60% of the dose being excreted unchanged at 6 h and 76% at 24 h.

Antileptazol activity and kinetics of clobazam and N-desmethyl-clobazam in the guinea-pig

The kinetic profiles and antileptazol activity of clobazam and its main metabolite were compared to assess the metabolite's contribution to the anticonvulsant activity of clobazam in the guinea-pig. The metabolite was less effective than the parent compound in terms of doses and active brain levels. However, the metabolite formed after clobazam administration accounted for the persistence of antileptazol activity in this animal species.

Kinetics of fenfluramine isomers in the rat

The kinetics of fenfluramine isomers were studied in the rat following oral doses of racemic fenfluramine. The data, analyzed using an analogue computer, indicate that the d-fenfluramine is metabolised and excreted at a slower rate than the 1-isomer, resulting in higher plasma and brain concentrations. The kinetic parameters of both isomers were dose-dependent. The rates of disappearance decreased as the dose was raised. The increase in brain area under the curves (AUC) was much greater than the increase of the dose. These findings suggested the rat has a limited capacity for disposition of fenfluramine.

Differential pulse polarographic determination of BCNU pharmacokinetics in patients with lung cancer

BCNU levels were determined by differential pulse polarography in 12 patients with lung cancer. A simple assay method for submicrogram quantities of nitrosoureas is described. The half-life of BCNU added to plasma in vitro was 1413 mins at 0 degrees C and 12 mins at 37 degrees C during incubation. BCNU kinetics in blood of treated patients was calculated using the two-compartment open model; the half-life of the drug was 1.4 mins in the first phase and 17.8 mins in the second. Mean distribution volume was 2.59 liters/kg and plasma clearance was 16.7 ml/min/kg.

Pharmacokinetics of hexamethylmelamine and pentamethylmelamine in mice

Plasma pharmacokinetics of hexamethylmelamine (HMM) and pentamethylmelamine (PMM) were investigated after ip administration of doses of 50 or 100 mg/kg to M5076/73A ovarian tumor-bearing C57BL/6J female mice. The half-life of HMM was 44.5-49 mins; the half-life of PMM was 7.6-8.7 mins. The area under the concentration-versus-time curve (AUC) was also much higher for HMM than for PMM. The AUC for the metabolite N2,N2,N4,N6-tetramethylmelamine (TMM) was seven to ten times higher than that of the parent compounds. After incubation with mouse liver microsomes and cofactors, the rates of metabolism of HMM and PMM were essentially the same. Plasma protein binding was 94%, 71%, and 50% for HMM, PMM, and TMM, respectively.

Differential adriamycin distribution to blood components

The differential distribution of doxorubicin (Adriamycin = AM) and daunorubicin (Daunomycin = DM) within the blood components, after an i.v. injection of 10 or 15 mg/kg of body weight, was investigated from its metabolites and quantified by means of the TLC scanning fluorescence technique. AM accumulated in the following order (of decreasing percentages): plasma and red cells (RBC), white cells (WBC), and platelets (PT), but the absolute amount of drug that reached each cell type was related to its relative volume. In the presence of higher blood concentrations (after injection of 15 mg/kg of body weight) the RBCs accumulated much more AM than the plasma, WBC, and PT; suggesting that the RBC fraction has a greater capacity to concentrate the drug. However, if the concentration of AM is expressed per unit volume of each component, a markedly higher value was observed for PT, and this was confirmed by in vitro results obtained by incubating blood in the presence of AM. DM seemed to be distributed on a percent basis to a greater extent than AM in the RBC fraction. Both compounds were taken up by blood cells, particularly platelets, to levels in excess of the extracellular concentration.

Effects of saccharin on primary humoral antibody production in rats

Rats for 25 to 54 days with diets containing high concentrations (1;2.5; 5%) of saccharin showed marked, dose-dependent suppression of primary humoral antibody production against heterologous erythrocytes. Phytohemagglutinin (PHA)-induced blastogenesis was not consistently affected by these saccharin-containing diets.

Neurochemical correlates of muricidal behavior in rats

Surgical, pharmacological or environmental manipulation are widely employed to induce muricidal behavior in naive laboratory male rats. The genetic predisposition of an animal strain to kill mice remains, however, an important factor to obtain the muricidal reaction. Data from the pertinent literature suggest that muricidal behavior may possibly be sustained by increased dopaminergic or catecholaminergic activity in the presence of reduced serotoninergic activity. The results here presented indicate, instead, that complete abolition of brain serotoninergic control, i.e., maximal depletion of brain serotonin, is just enough per se to induce muricidal activity. Further, this chemically-induced muricidal activity goes well beyond any pre-existing strain predisposition to kill mice or not.

Urinary excretion of an uracilic metabolite from caffeine by rat, monkey and man

Caffeine (C) metabolism has been studied in rat, monkey (Macaca cynomolgus) and man after oral administration of the compound. Eleven metabolites were quantified in urine; particular attention has been drawn to 4-amino [5-formyl methylamino]1,3-dimethyl uracil (ADMU) because of its structural analogies with 5-fluorouracil. The rat has been found to produce a much larger fraction of ADMU (about 30%) in respect to monkey an man (1-2%). The potential toxicological implications of this findings are discussed.

p-Chlorophenylalanine-induced muricidal aggression in male and female laboratory rats

p-Chlorophenylalanine (pCPA), a potent inhibitor of serotonin synthesis, specifically depletes brain serotonin in a dose-dependent manner. The resulting impairment of serotonergic inhibitory control of the brain is considered responsible for the consequent muricidal aggression that arises in pCPA-treated rats independent of their strain-dependent genetic predisposition and sex propensity to display this behavior. Judging from the data obtained, the minimal impairment of serotonergic inhibitory control required to induce consistent muricidal aggression in rats of both sexes of the strains considered, corresponds to a brain serotonin depletion of about 55-60%.

Effect of oral monosodium glutamate on glutamic acid levels in the nucleus arcuatus of the hypothalamus and on serum osmolality of adult and infant mice

Monosodium glutamate (MSG) given by gavage to 7-day-old mice at 2 g/kg body weight (b.wt.) as a 20% solution w/v resulted in a 27% increase in the glutamic acid (GA) content in the nucleus arcuatus of the hypothalamus (NAH). When MSG was administered by gavage to adult mice at 4 g/kg b.wt. as a 20% solution w/v, GA levels in NAH remained unchanged. Serum osmolality, measured after oral MSG, was elevated in infant mice but was unaffected in adults.

Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on macrophage and natural killer cell-mediated cytotoxicity in mice

C57Bl/6 J mice (6-8 weeks old) were given single i. p. doses (1, 2, 6 and 30 micrograms/kg) of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) and macrophage-mediated and natural killer (NK) cell-mediated cytotoxicity was evaluated at different times after treatment. Peritoneal macrophage cytolytic activity was measured as 3H-thymidine release from prelabelled mKSATU5 target cells in a 48 hours assay; macrophage-mediated cytostasis was assessed in terms of inhibitions of 3H-thymidine uptake by SL2 lymphoma cells. Spleen NK activity was measured using 51Cr-labelled YAC-1 lymphoma cells as targets. TCDD did not modify spontaneous macrophage-mediated and NK cell-mediated cytotoxicity per unit number of effector cells nor did it affect the macrophages' capacity to express increased cytolytic and cytostatic activity in the presence of endotoxin. Lower numbers of peritoneal macrophages and splenocytes were recovered from TCDD treated mice. Thus the total numbers of lytic units recovered from animals exposed to TCDD were lower than controls. Impairment of these cellular effector mechanisms, due to cell loss rather than inhibition of function, might play a role in the lowered resistance to bacterial infection of mice given TCDD and in the carcinogenic and cocarcinogenic activity of this chemical.

Plasma levels of cyclophosphamide in patients under polychemotherapeutic regimens

Plasma levels of non metabolized CPA were measured in two groups of lung cancer patients receiving polychemotherapy. There was extreme variability in the data obtained during the first hour after CPA administration. After this period of time a wide range of T 1/2 was found particularly in one of the two groups of patients. "Border-line" patients (with T 1/2 at the upper or lower limits of the range found) are discussed as regards the possible influence of ancillary treatment.

Metastasizing capacity of tumour cells from spontaneous metastases of transplanted murine tumours

We investigated the metastasizing capacity of spontaneous lung metastases from the MN/MCA1 and mFS6 sarcoma, the B16 melanoma and colon 26 carcinoma. Spontaneous metastases at other visceral organs (liver, spleen, kidney, ovary, uterus) from the M5076/73A (M5) ovarian carcinoma and colon 26 carcinoma were also studied. Tumour cells from individual spontaneous metastases were used immediately after isolation from the normal parenchyma (mFS6, M5 and colon 26) and/or after 1 s.c. passage in syngeneic mice (MN/MCA1, mFS6, B16 and M5). Spontaneous metastases were examined for all tumours and their secondaries after i.m. or s.c. inoculation of tumour cells; artificial lung colonies were measured after i.v. injection only of cells from the primary mFS6 and MN/MCA1 and B16 or their spontaneous metastases. Individual spontaneous metastases were to some extent heterogeneous in their metastatic potential, a minority of the secondaries having greater or lesser metastatic capacity than the appropriate primary. Overall, tumour cells from spontaneous metastases did not show greater metastasizing capacity than primary neoplasms, nor was there evidence that metastases from specific organs (e.g. spleen and kidney) tended to home to the specific anatomical sites from which they were originally isolated. These observations in a series of murine tumours of different histology, transplantation history and pattern of metastasis, do not support the hypothesis that metastases are the ultimate expression of strong selection of variant cells with greater intrinsic metastatic potential, pre-existing within the primary tumour.