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Biomedical subjects

S Garattini

Publications and source records attributed to S Garattini.

At least 199 records · Page 11Linked to original sources
PubMed1984

Kinetics and metabolism of theobromine in male rats.

On the basis of general pharmacological information (blood cells/plasma partition, plasma protein binding) and using HPLC as the principal analytical method, we investigated the kinetics and metabolism of theobromine (a caffeine metabolite) in male rats after a single dose and after a 2 week chronic application. Doses in both conditions varied between 1 and 100 mg/kg. In in vitro and in vivo the fraction of theobromine unbound to plasma proteins averaged 0.90 over a wide range of concentrations. No significant difference was found in the pharmacokinetic profile of the drug after acute or chronic treatment at different doses except for a reduction in the absorption rate constant as the dose increased. AUC values increased in proportion to the dose. The 2 treatment schedules were also similar as regards metabolism, at least 50% of the administered dose of theobromine being excreted unchanged, and 25% as 6-amino-5-[N-methyl- formylamino ]1-methyluracil. Only at the highest doses was there a tendency for theobromine to accumulate at the expense of its major metabolite (a uracil compound).

Animals↗
PubMed1984

Kinetics and metabolism of theobromine in male and female non-pregnant and pregnant rabbits.

The kinetics and metabolism of theobromine (3,7- DMX ) were investigated in male rabbits after a single oral dose and 14 days oral dosing at 1, 5, 10, 50 and 100 mg/kg/day. Female non-pregnant and pregnant rabbits were also studied after single oral doses of 1, 5 and 50 mg/kg. No significant difference was found in the pharmacokinetic profile of 3,7- DMX due to either sex, pregnancy or after chronic oral administration for 14 days. Intravenous (i.v.) administration of 3,7- DMX at 1 and 5 mg/kg resulted in calculated kinetic parameters in close agreement with oral doses. Irrespective of sex, there was a reduction in the absorption rate constant as the dose increased, coupled with a linear dose-related increase in AUC values. No qualitative difference in the metabolism of 3,7- DMX in the rabbit was observed as linked to sex, pregnancy or treatment schedule. Twenty-five percent of the administered dose of 3,7- DMX was excreted unchanged, the major metabolite being 7-methylxanthine (40%). There appeared to be a shift in the metabolic pathway at 100 mg/kg/day in the males and at 50 mg/kg/day in the females with more unchanged 3,7- DMX excreted. Only at these highest doses (100 mg/kg for males and 50 mg/kg for pregnant rabbits) was there a tendency toward accumulation.

Animals↗
PubMed1984

A pharmacokinetic and platelet function study of the combined administration of metoprolol and sulfinpyrazone to healthy volunteers.

In a double-blind study on healthy subjects who underwent three 3-week periods of treatment with metoprolol (M) + sulfinpyrazone (S), M + placebo, and S + placebo, pharmacokinetics and plasma levels of M were not affected by concurrent administration of S. Analysis of variance change-over demonstrated a significant difference between treatments only for serum uric acid levels. Analysis of post-treatment and baseline data within each treatment showed: decreased platelet count by M, lowered serum 6-keto PGF1 alpha by all three treatments, decreased serum TXB2 generation and arachidonic acid-induced platelet aggregation by S + M. No negative interaction between S + M was found.

Adult↗
PubMed1984

Neurochemical effects of minaprine, a novel psychotropic drug, on the central cholinergic system of the rat.

Minaprine, a novel psychotropic drug with antidepressant, anticataleptic and antiaggressive properties, produced an increase in rat brain regional acetylcholine content at a subconvulsant dose of 30 mg/kg IP. The greatest increase (60%) was produced in the striatum, whereas an increase of about 35% was obtained in the hippocampus and the rest of the cortex. A small but significant increase of 14% was also found in the midbrain-hindbrain region. Minaprine decreased choline content only in the striatum. No tolerance to acute challenge was observed after 10-day chronic treatment. In vitro, the drug had no effect on striatal choline acetyltransferase activity up to a concentration of 160 microM and only weakly displaced (3H) dexetimide from its specific muscarinic receptor binding sites in striatum (IC50, 2 X 10(-4) M). After in vivo administration the drug did not affect sodium-dependent high affinity choline uptake by a hippocampal homogenate. On the other hand, the drug inhibited both striatal and hippocampal acetylcholinesterase activity at high (40-160 microM) concentrations in vitro. In vivo the drug produced a brief (5 min), small (18%) decrease in the enzymic activity which corresponded in time to the peak drug level attained in the brain, but was not concomitant with a change in striatal acetylcholine content. By contrast, the increase in striatal acetylcholine appeared after 30 min when there was no longer inhibition of acetylcholinesterase activity and when the level of minaprine in brain was reduced by 78%. Blockade of dopamine receptors by pimozide pretreatment partially prevented the increase in striatal acetylcholine produced by minaprine, whereas interference with cholinergic or serontonergic neurotransmission was without effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1984

Drugs: guide and caveats to explanatory and descriptive approaches--I. A critical evaluation of the current status of antidepressant drugs.

The development of knowledge about the mechanism of action of tricyclic and the so-called "atypical" antidepressants is reviewed. The discovery of clinically active antidepressants with little or no effect on noradrenaline or serotonin uptake has disproved the widely accepted concept that inhibition of monoamine uptake is a prerequisite for antidepressant activity. Another serious objection to this hypothesis is the fact that blockade of monoamine uptake occurs in a matter of minutes after administration while 2-3 weeks of repeated treatment are necessary for the clinical antidepressant effect. Nevertheless, the effect of repeated treatment with antidepressants is compatible with the hypothesis that changes in central monoamine transmission are involved in the clinical activity of these drugs. Major changes in monoamine function after repeated treatment with antidepressants include: a decrease in number of beta-adrenergic receptors, increased sensitivity of alpha 1-adrenoreceptors, down-regulation of serotonin2 receptors, increased sensitivity to behavioural and electrophysiological effects of serotonin agonists, subsensitivity of presynaptic dopamine receptors and enhanced dopamine function. It remains to be clarified whether some of these changes play larger roles than others or whether they all contribute to the antidepressant activity. In spite of some attractive suggestions, there is still no clear evidence that changes in different monoaminergic systems influence different features of the depressive syndrome.

Animals↗
PubMed1984

Effects of disodium etidronate in murine tumor models.

This study was designed to elucidate the effect of ethane-1-hydroxy-1,1-diphosphonate (EHDP) in experimental rodent tumors. EHDP had no antitumor activity against the L1210 leukemia implanted i.p. and against sarcoma 180, Lewis lung carcinoma (3LL) and Walker 256/B carcinoma injected i.p., s.c. or i.m. respectively. EHDP did not interfere with the antitumor activity of commonly used conventional chemotherapeutic agents (adriamycin, cyclophosphamide, 5-fluorouracil, bis-chloroethylnitrosourea) in the L1210 and 3LL models. EHDP reduced proportionally to the dose the hypercalcemia and hypercalciuria due to the Walker 256/B carcinoma growth. In an effort to evaluate whether EHDP-treated osseous tissues were more refractory to tumor growth, cells from sarcoma 180 and 3LL carcinoma were implanted intratibially (i.t.). Growth of 3LL cells was not consistently affected by EHDP, whereas a modest, but significant, growth inhibition was consistently observed with sarcoma 180 injected i.t. Growth of sarcoma 180 implanted i.p. or s.c. was not reduced by this drug, thus suggesting that inhibition of i.t. sarcoma 180 was in fact related to alterations of osseous tissues by EHDP. Inoculation of Walker 256/B carcinoma intra-aortically resulted in osteolytic bone lesions in the hind limbs. EHDP inhibited the formation of bone metastasis under these conditions.

Animals↗
PubMed1984

Biochemical effects of minaprine on striatal dopaminergic neurons in rats.

The biochemical effects of minaprine, a new psychotropic drug, were investigated on striatal dopaminergic neurons in the rat. Minaprine did not displace [3H]spiperone in-vitro binding from striatal membranes but had clear effects on dopamine (DA) metabolites. Homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) were significantly decreased in a dose-dependent manner after intraperitoneal administration of minaprine 30 min before killing. In rats injected with minaprine 15 mg kg-1 i.p. at different intervals, the decrease in striatal HVA and DOPAC was time-dependent and a concomitant rise in 3-methoxytyramine (3-MT) concentrations was observed. The maximum of these effects was reached 30 min after minaprine. When administered 5 min after a monoamineoxidase (MAO) inhibitor (pargyline, 100 mg kg-1 i.p.) and 30 min before killing, minaprine did not affect pargyline-induced changes in HVA, DOPAC and 3-MT levels. This together with other data suggests that minaprine affects DA metabolism by acting, at least partially, at presynaptic level through in-vivo inhibition of MAO activity.

Animals↗
PubMed1984

Increased number of brain benzodiazepine receptors after in-vivo administration of estazolam to rats.

Estazolam significantly increased the Kd of [3H]flunitrazepam in-vitro, like other benzodiazepines (BDZs) acting competitively at the receptor site. At variance with other BDZs, estazolam significantly raised the Bmax for [3H]flunitrazepam, at concentrations lower than its Ki for BDZ receptors. This effect may be responsible for the observed increase in [3H]diazepam binding after in-vivo administration of estazolam to rats.

Animals↗
PubMed1984

Long-acting and short-acting benzodiazepines in the elderly: kinetic differences and clinical relevance.

A review of available information about the pharmacokinetics of pro-nor-diazepam-like compounds in the elderly shows substantial impairment of the metabolism compared to oxazepam-like benzodiazepines, which are metabolized with virtually no change in this age group. Results of clinical trials point in the same direction, although small numbers of patients, different criteria for measuring clinical benefit and adverse reactions and different dosages for various periods of time make the comparison difficult. Qualified clinical guidelines are mainly to reduce dosage and use oxazepam-like compounds in the elderly, but routine clinical practice does not seem to apply these recommendations. Further research is therefore needed, mainly in the area of clinical practice, to describe the 'real' situation of benzodiazepine prescription for in-patients and out-patients in terms of risk-benefit ratio of drug treatment and to monitor the changes occurring when a more rational approach is introduced as regards the need for treatment, dose and duration of treatment.

Adult↗
PubMed1984

d-Fenfluramine and salbutamol: two drugs causing anorexia through different neurochemical mechanisms.

Recent studies on some neurochemical and functional effects of d-fenfluramine and salbutamol in rats were summarized. It was found that d-fenfluramine releases serotonin almost exclusively from a reserpine-sensitive pool, but this is not the only mechanism by which it reduces food intake, as reserpine did not change its anorectic activity. The fact that d-norfenfluramine, the active metabolite of d-fenfluramine, uses mainly a reserpine-insensitive pool may help explain the failure of reserpine to reduce d-fenfluramine's effect on food intake. On the other hand, metergoline and chlorimipramine significantly reduced the effect of d-fenfluramine suggesting that drug's uptake into serotonin-confining neurons and serotonin release are important for the anorectic activity. The ability of d-fenfluramine to enhance serotonin function leads to a pattern of effects on various forms of eating that distinguishes this drug from d-amphetamine. In particular, studies with food-rewarded runway behaviour have clearly shown that d-fenfluramine reduces motivation for food whereas no such effect is clear for d-amphetamine. Salbutamol, a beta-adrenergic stimulant, was shown to reduce food intake in rats in a dose-dependent manner through a mechanism which seems to involve beta-adrenergic sites in the brain. The mechanism of action of salbutamol seems to be different from that of d-amphetamine since no cross-tolerance between the two drugs was found as regards their anorectic activity. Moreover, salbutamol and d-amphetamine affected differently some aspects of feeding behaviour in rats.

Albuterol↗
PubMed1984

Pharmacokinetic studies of anticancer drugs in tumor-bearing animals.

The pharmacokinetics of antitumor agents is a relatively recent area of research, as lack of proper specific methodology for monitoring drug levels has always hampered major efforts. Although the relationship among administered dose, tissue concentration, and therapeutic and/or toxic effects remains extremely complex, a series of experimental and clinical studies provides information on the pharmacokinetic behavior of most anticancer agents in different conditions. This review article describes examples selected from the work of this Institute on several points which may be relevant to the use of these compounds: (a) factors influencing pharmacokinetics, such as genetic constitution of the host, presence of the tumor, dose, route of administration and schedule, organ insufficiency, and interactions with other drugs; (b) drug distribution in host tissues in relation to toxic effects; (c) drug distribution to secondary tumors (metastases); (d) importance of active metabolites; and (e) drug distribution and binding to intracellular target sites. An analysis of these factors shows that many aspects are still very poorly understood and require considerable further study.

Animals↗
PubMed1983

Polarographic assay of submicrogram quantities of cis-dichlorodiamineplatinum (II) in biological samples.

Differential pulse polarographic assay of the antineoplastic agent cis-dichlorodiamineplatinum II and its analogues was performed after acid oxidative hydrolysis (HClO4, HNO3, HCl) of biological samples (plasma, tissue homogenates, urine) and reaction with ethylenediamine. Platinum levels and kinetics were determined in blood and urine of patients with non-oat-cell lung carcinoma. Detection limit of the polarographic assay was 0.5 ng platinum; analytical error was +/- 3%. Levels of free cis-dichlorodiamineplatinum (II) in plasma fell in samples stored at -20 degrees C; the half-life of free drug was 38 h.

Carcinoma, Bronchogenic↗
PubMed1983

Dopaminergic effects of buspirone, a novel anxiolytic agent.

The novel anxiolytic drug buspirone raised striatal levels of the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) 1 hr after oral administration. This effect was dose-dependent with a peak at 60 min. No changes were observed in the levels of 3-methoxytyramine (3MT), the extraneuronal metabolite of dopamine. Noradrenaline, serotonin and its metabolite 5-hydroxyindoleacetic acid (5HIAA) were not affected. Buspirone displaced [3H]spiroperidol from striatal binding sites, with an IC50 (1.8 x 10(-7) M), comparable to that of clozapine (IC50 = 1.4 x 10(-7) M) but considerably lower than that of haloperidol (4.7 x 10(-9) M). Buspirone was only a weak inhibitor of dopamine-stimulated adenyl cyclase. Buspirone was not active on the binding of trifluoperazine to calmodulin and did not modify calmodulin-induced activation of phosphodiesterase (PDE). Repeated administration of buspirone did not increase the number of DA receptors. These data show that, although buspirone has antidopaminergic activity, it can hardly be classified as a classic neuroleptic agent.

Animals↗
PubMed1983

Immunosuppressive effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin in strains of mice with different susceptibility to induction of aryl hydrocarbon hydroxylase.

Mouse strains with different susceptibility to aryl hydrocarbon hydroxylase (AHH) induction and with different levels and/or affinity for a specific cytosolic binding protein ("receptor") were used to investigate the immunosuppressive effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Humoral antibody production was strongly inhibited in C57Bl/6 and C3H/HeN mice (more susceptible strains) with very low, single doses of TCDD (1.2 micrograms/kg), while other strains (DBA/2 and AKR) required higher doses (at least 6 micrograms/kg) to be partially suppressed. Longer exposure (8 weeks) did not increase the sensitivity of DBA/2 mice. A good correlation between the degree of enzyme inducibility and immunosuppression was observed in studies with B6D2F1 mice and backcrosses. Similar results were obtained with 2,3,7,8-tetrachlorodibenzofuran (TCDF), the most powerful competitor for TCDD "receptor" in vitro and in vivo. TCDD immunotoxic effects appeared to be associated with the presence of a specific cytosolic binding protein which mediates AHH induction.

Animals↗
PubMed1983

In vitro and in vivo cytotoxicity of possible uracil metabolites of methylxanthines.

The present study was designed to elucidate the cytotoxic potential of 8 possible substituted uracilic metabolites of methylxanthines. 5-Fluorouracil (5-FU) was used as a reference uracil analogue with cytotoxic activity. Substituted uracil derivatives examined in this study did not affect the proliferative capacity of PHA-stimulated rat lymphocytes, murine L1210 leukaemia and rat chondrocytes. Caffeine had some growth inhibitory activity of extremely high concentrations (greater than 100 micrograms/ml). In vivo administration of 6-amino-5[N-methyl-formylamino]1,3-dimethyluracil (1,3,7-TAU) and 6-amino-5[N-acetylamino]3-methyluracil (7-A3-MAU) caused a transient short-lived reduction of L1210 tumour cell numbers. These observations do not appear to support the hypothesis that substituted uracils are involved in the toxicity of high doses of caffeine in rats.

Animals↗
PubMed1983

Pyroglutamate kinetics and neurotoxicity studies in mice.

Plasma and brain kinetics of L-glutamic (GA) and L-pyroglutamic (PY) acids were studied after oral administration of monosodium glutamate (MSG) or pyroglutamate to adult mice. Oral MSG (0.5 g/kg) increased plasma GA and PY levels 4.5 and 1.8 times, respectively. A small increase in brain PY (1.3 times the basal level) but not in brain GA, was observed. Oral administration of pyroglutamate (0.5 g/kg) increased plasma PY levels 56 times in adult mice and 69 times in infant mice. No lesions in the arcuate nucleus of the hypothalamus were observed when pyroglutamate was administered orally to infant mice at doses of 2 and 4 g/kg.

Animals↗
PubMed1983

Plasma pyroglutamic acid levels after oral administration of monosodium glutamate to human volunteers.

Plasma levels of pyroglutamic (PY) and glutamic (GA) acids have been measured after oral administration of monosodium glutamate (MSG) to 6 human volunteers. MSG (43 mg/kg) was administered either after an overnight fast or immediately after a normal meal. In fasting subjects plasma GA peak levels were about 2.3 times the basal levels whereas the increase in plasma PY levels were only 1.5-fold. When MSG was administered with a meal plasma GA levels were raised, to a lesser extent, while no increase could be observed in plasma PY.

Administration, Oral↗