Interaction of gentamicin with atrial natriuretic polypeptide receptors in renal cells

Anti-inflammatory action of gentamycin through inhibitory effect on neutrophil NADPH oxidase activity

The effects of gentamycin on the NADPH oxidase (EC 1.6.99.6) from human neutrophils in both whole-cell and fully soluble (cell-free) systems were investigated. Gentamycin was found to inhibit, concentration-dependently, the superoxide generation of neutrophils exposed to phorbol myristate acetate in a whole-cell system and the activation of superoxide-generating NADPH oxidase by sodium dodecyl sulfate in a cell-free system. The concentrations of the drug required for 50% inhibition of the oxidase (IC50) were 150 microM in the whole-cell system and 10 microM in the cell-free system. In addition, in the cell-free system, the drug did not change the Km value for NADPH of the oxidase. However, gentamycin did not the superoxide generation of NADPH oxidase after its activation in the cell-free system, suggesting that the drug do not have superoxide-scavenger action. These results suggest that gentamycin, an aminoglycoside antibiotic, may exhibit an anti-inflammatory action due to inhibition of neutrophil NADPH oxidase activation.

Renal handling of tobramycin in the isolated perfused rat kidney

The renal handling of tobramycin (TOB), an aminoglycoside antibiotic (AG), was studied using a single-pass isolated perfused rat kidney with moment analysis. In the bolus administration study at tracer concentration (7.4 microM), 32% of the glomerular-filtrated TOB remained in the lumen, but no TOB was found in the vein. This ratio of the luminal uptake was reduced in a dose-dependent manner. Other aminoglycosides such as gentamicin inhibited this uptake, but tetraethylammonium and glucosamine had no effect. In addition, under the alkalinuria condition, TOB uptake was decreased to 67% of the control value. This indicated that TOB has mainly been taken into the renal epithelial cells from their luminal site and that this uptake process was saturable and specific for AGs which have more than one cationic group. The present findings should be helpful in developing a method to reduce the nephrotoxicity of AGs and to identify their toxicity mechanisms.

Partial characterization of allatinhibin, a neurohormone of Manduca sexta

During the last larval stage, corpora allata (CA) of Manduca sexta are inactivated by a factor from the brain. Apparently the same factor (allatinhibin, AI) is secreted by day 4 Vth instar brains kept overnight in Grace's medium. AI is rapidly inactivated by heat or acid but withstands exposure to alkali and can be recovered after freezing and lyophilization. Exposure to pronase, chymotrypsin, carboxypeptidases-A and -Y, as well as leucine aminopeptidase eliminated AI activity completely, whereas after exposure to trypsin and protease XVII-S, some residual activity remained. Inactivation by pyroglutamate aminopeptidase is interpreted as being due to prolinase activity of this enzyme. Incubation of CA with gentamicin, an aminoglycoside antibiotic, affects neither their ability to produce JH in vitro nor their viability in implantation assays. However, AI did not inactivate CA in the presence of low concentrations of gentamicin. This effect was used to guard against false positive assay results possibly produced by allatotoxic contamination. AI was purified by chromatography on Sephadex G-25. All activity recovered emerged from the columns in intermediate fractions with an apparent M(r) of 1,000-2,000.