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Biomedical subjects

A Trouet

Publications and source records attributed to A Trouet.

At least 55 records · Page 3Linked to original sources
PubMed1984

Cellular pharmacology of amino acid derivatives of daunorubicin and doxorubicin in suspension of renal proximal tubules.

One approach currently being used to target drug action selectively to specific cells and tissues is to link active drugs to proteins and peptides that are preferentially recognized by, distributed to or activated by the target cells. Inasmuch as the kidney proximal tubule cells are very active in recapturing and catabolizing peptides and proteins which appear in the glomerular filtrate, we have examined the cellular pharmacology of daunorubicin (DNR) and doxorubicin (DOX) and selected amino acid and dipeptide derivatives in suspensions of rabbit renal proximal proximal tubules. The tubules accumulated the DNR series of drugs and their metabolites to a greater extent than the DOX series. Although all of the amino acid derivatives of these drugs entered the cells for sequestration and metabolism, the dipeptide derivative, alanyl-leucyl-DNR, was not detected within the cells. Using high-performance liquid chromatography to quantify the various metabolites and isopycnic centrifugation of tubule-derived post-nuclear supernates in linear sucrose gradients to resolve various subcellular organelles, the subcellular sites of metabolism of these drugs were examined. A NADPH-dependent reduction of the C-13 carbonyl group of the parent drugs, which was the primary route of metabolism, was localized to the cytoplasm. Formation of aglycones generated by the cleavage of the daunosamine moiety from the anthracycline core followed the microsomal marker, NADPH-cytochrome reductase, in the sucrose gradients. Removal of the terminal amino acid from alanyl-leucyl-DNR was tentatively assigned to a cysteine-requiring enzyme on the plasma membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1983

Cultivation of rat cerebellar cells under conditions of optimal oxygen supply.

A method is described for the cultivation of essentially small cerebellar neurones under optimal oxygen supply. Cerebellar cells were seeded onto polylysine-coated dishes equipped with a gas-permeable bottom (Petriperm). Under these conditions, cells migrated to form small groups and developed dense networks of fibres covering the entire bottom of the dish. Contamination with non-neuronal cells was restricted to fibroblasts (less than 0.1%), oligodendrocytes (less than 1%) and astrocytes (approximately 6%), even after prolonged cultivation (15 days).

Animals↗
PubMed1983

Iron mobilization from cultured hepatocytes: effect of desferrioxamine B.

When cultured rat hepatocytes prelabelled for different times at 37 degrees with 59Fe are reincubated for 1 hr in a fresh medium, radiolabelled iron is released in the washout medium as a function of the prelabelling time, and behaves like low molecular weight material on isokinetic centrifugation in sucrose gradients. When apotransferrin or desferrioxamine B are present in the reincubation medium, the kinetics of iron release are similar but the absolute amounts of radiolabelled iron found in the culture medium are much greater. In the presence of apotransferrin, most of the 59Fe released from the cells distributes as transferrin whereas with desferrioxamine B, almost all the 59Fe is extracted by benzyl alcohol indicating its chelation by the drug. Cell fractionation data indicate that iron accumulated by hepatocytes is rapidly incorporated into cytosol ferritin, and this seems to be a preferred source of iron for the chelator.

Animals↗
PubMed1982

Transferrin protein and iron uptake by cultured hepatocytes.

The binding and uptake of 59Fe-loaded 3H-labelled rat transferrin by cultured rat hepatocytes was investigated. At 4 degrees C, there is no evidence for a specific binding of transferrin which could be related to the association of neo-synthesized transferrin with plasma membrane receptors. At 37 degrees C, iron uptake is much more important than transferrin uptake; it proceeds linearly over the time of incubation, is largely proportional to the extracellular transferrin concentration, and is compatible with uptake by fluid phase endocytosis. The difference observed between iron and transferrin uptake implies the existence of a mechanism allowing the reutilization of transferrin after iron delivery.

Animals↗
PubMed1982

The disposition of free and liposomally encapsulated antimalarial primaquine in mice.

Plasma clearance, urinary excretion and tissue distribution of radiolabeled free (FPQ) and liposome-entrapped Primaquine (LPQ) in mice were monitored for 2 hr following intravenous administration. FPQ is eliminated very rapidly from the plasma and excreted predominantly in the urine, probably largely in a metabolized form. In decreasing order of magnitude, pronounced accumulation of label occurs in the liver, kidneys, lungs and skeletal muscle. Less than 1 per cent of the total initial dose is recovered in other tissues. Partial erythrocytic sequestration results in drug levels higher and more persistent in blood cells than in the plasma. Compared to the free drug form, Primaquine entrapped within negatively charged liposomes of the cholesterol-rich multilamellar type exhibits a prolonged plasmatic half-life and, within the observation period, excretion is 8-fold reduced. Liver accumulation of label is doubled, accounting for close to 50% of the injected dose; splenic uptake is tripled, while accumulation in the lungs, kidneys, heart and brain is drastically reduced. These differences in pharmacodynamic behaviour may explain why liposomal entrapment leads to diminished acute Primaquine toxicity.

Animals↗
PubMed1982

Accumulation and metabolism of new anthracycline derivatives in the heart after IV injection into mice.

In an attempt to establish a relationship between the pharmacokinetics in mouse heart of new anthracycline derivatives and their potential chronic cardiotoxicity and on this way to provide a useful and economical test for screening of new analogs, we followed the accumulation and metabolism of six anthracyclines in the mouse heart after single IV administrations of these drugs at equimolar doses. We found that the six drugs, i.e., daunorubicin (DNR), doxorubicin (DOX), rubidazone (RBZ), detorubicin (DET), N-L-leucyl-DNR (LEU-DNR) and N-L-leucyl-DOX (LEU-DOX), accumulate at various levels in the cardiac tissue and are metabolized to different extents, leading to the appearance in the heart of variable amounts of DNR or DOX. The total exposure of the mouse heart, as evaluated by calculation of the areas under the CXt curves, can be correlated qualitatively with the chronic cardiotoxicity of the six anthracyclines, as recently determined in the rabbit model. We therefore think that our study provides a simple, rapid, and inexpensive predictive test for the screening of new analogs for potential cardiotoxicity. Moreover, it offers the advantage of using the same species for determining the most favorable ratio between therapeutic activity and toxic side-effects.

Animals↗
PubMed1982

Cellular pharmacokinetics of aclacinomycin A in cultured L1210 cells. Comparison with daunorubicin and doxorubicin.

Aclacinomycin, which is more lipophilic than daunorubicin and doxorubicin, is taken up and released more rapidly and extensively by L1210 cells. After 5 h of incubation 91% of aclacinomycin is found in the nuclei of L1210 cells and the drug present in the post-nuclear fraction is distributed between the lysosomes and the cytosol. After an incubation of 5 h aclacinomycin decreases the density of the lysosomes. This effect is not observed either with doxorubicin or daunorubicin or when the cells are incubated with aclacinomycin for only 30 min.

Aclarubicin↗
PubMed1982

Plasma levels of doxorubicin after IV bolus injection and infusion of the doxorubicin-DNA complex in rabbits and man. Comparison with free doxorubicin.

When injected rapidly IV into rabbits, the plasma levels of free DOX decreased biphasically and the drug was distributed in a volume greater than the body volume. When given as a DNA complex, the area under the concentration versus time curve was increased 10-fold and the distribution volume reduced more than 100-fold. The DOX-DNA complex infused both in rabbits and in human patients reached steady state-concentrations 10 and 20 times higher, respectively, than free DOX infusion, and the distribution volumes were reduced accordingly. These results confirm that the observed lower cardiotoxicity of the DOX-DNA complex arises despite higher plasma concentrations of the drug.

Animals↗
PubMed1982

Evidence for a continual exchange of 5'-nucleotidase between the cell surface and cytoplasmic membranes in cultured rat fibroblasts.

Approximately 40% of the 5'-nucleotidase activity in cultured rat embryo fibroblasts was patent, as judged by enzymatic assays comparing the activity of intact cells with detergent-solubilized cells. The patent activity was inhibited when cells were incubated with anti-5'-nucleotidase serum at 2 degrees C, whereas latent activity (calculated as the difference between total and patent activity) was not. Latent activity was inhibited by antibody when the antiserum was added directly to detergent-solubilized cells or when cells were cultured in the presence of antiserum for several hours. Patent activity was inhibited by antibody, and cells were returned to culture in antibody-free medium; after 12 hr, 30% of the total activity was expressed in intact cells and 60% of the anti-5'-nucleotidase, assayed by the binding of sheep antirabbit antibodies to intact cells, was lost from the cell surface, indicating an exchange of 5'-nucleotidase between the latent and patent compartments. Cytochemical studies showed that the patent activity was located on the cell surface and that latent activity was present in cytoplasmic vacuoles and vesicles, and in the Golgi complex. Over 30% of the anti-5'-nucleotidase internalized during 6 hr in culture returned to the cell surface after a further 9 hr, indicating a continual exchange of the enzyme between the cell surface and cytoplasmic membranes.

Animals↗
PubMed1982

A covalent linkage between daunorubicin and proteins that is stable in serum and reversible by lysosomal hydrolases, as required for a lysosomotropic drug-carrier conjugate: in vitro and in vivo studies.

Daunorubicin (DNR) has been conjugated to succinylated serum albumin by an amide bond joining the amino group of the drug and a carboxyl side chain of the protein either directly or with the intercalation of a peptide spacer arm varying from one to four amino acids. During in vitro incubation with lysosomal hydrolases, intact DNR could be released extensively only from conjugates prepared with a tri- or tetrapeptide spacer arm. These latter conjugates remained very stable in the presence of serum. When tested in vivo against the intraperitoneal form of L1210 leukemia, the conjugates in which DNR was linked to serum albumin directly or via one amino acid were completely inactive but the conjugate with a dipeptide spacer arm was not more active than free DNR. In parallel with the in vitro studies, the best therapeutic results were obtained with the conjugates formed with tri- and tetrapeptidic spacer arms; they were much more active than DNR, inducing a high percentage of long-term survivors. Thus, use of a tri- or tetrapeptide spacer arm is essential to obtain DNR-protein conjugates that remain stable in serum and from which DNR can be released through the action of lysosomal hydrolases. The in vivo results suggest, moreover, that these conjugates are endocytosed by L1210 cells and that DNR is released intracellularly after digestion by lysosomal enzymes. This conjugation method can be applied to other drugs possessing a free amino group and to various potential carriers, such as antibodies, polypeptide hormones, and glycoproteins, that have amino or carboxyl side chains.

Albumins↗
PubMed1982

Comparative cardiac and renal toxicity of daunorubicin in the rat and rabbit.

A direct comparison of the cardiac and extracardiac effects of repeated daunorubicin administration in the rat and rabbit demonstrated a basic similarity in the cardiac myocyte response. The rat, however, appears to develop a more severe drug-related nephropathy, resulting in widespread soft tissue mineralization that includes vessels and the myocardium. These findings suggest that the severity and development of acute and chronic anthracycline-induced cardiac lesions may, in the rat, be related or dependent, in part, on concomitant nephrotoxicity.

Animals↗