Gentamicin inhibits carrier-mediated dipeptide transport in kidney

1996 ◽  
Vol 270 (3) ◽  
pp. F531-F538
Author(s):  
H. A. Skopicki ◽  
D. Zikos ◽  
E. J. Sukowski ◽  
K. A. Fisher ◽  
D. R. Peterson
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Morphological Changes ◽  
Membrane Vesicles ◽  
Renal Brush Border Membrane ◽  
Dipeptide Transport ◽  
Vitro Effect ◽  
Renal Brush Border

The effect of gentamicin on transport of pyroglutamylhistidine (pGlu-His) was examined in rabbit renal brush-border membrane vesicles (BBMV). Gentamicin, an aminoglycoside antibiotic, is limited in its usage because of nephrotoxicity characterized in part by transport defects in the proximal tubule. Since there is no information regarding the effects of gentamicin on renal peptide carriers, uptake of [3H]pGlu-His was measured in BBMV following either in vivo or in vitro exposure to the antibiotic. One hour after in vivo administration, the maximal rate (Vmax) for pGlu-His transport was significantly reduced in isolated membrane vesicles washed free of the drug, but the apparent Michaelis constant (Km) was unaltered. Coincubation of membranes with gentamicin during measurements of pGlu-His uptake had a similar effect, causing a significant decrease in the Vmax but not the Km of transport. The addition of 5 mM magnesium to the uptake medium prevented the in vitro but not the in vivo effect. The data indicate that high doses of gentamicin inhibit the capacity but not the affinity of dipeptide transport in the kidney, prior to morphological changes which typify acute tubular necrosis. The in vitro effect is rapid and involves a direct action of gentamicin on the brush-border membrane. The in vivo experiments show that toxicity may be prolonged and remains following removal of the drug from the renal brush border.

Actions of NAD+ on renal brush border transport of phosphate in vivo and in vitro

1985 ◽  
Vol 249 (6) ◽  
pp. F948-F955 ◽  
Author(s):  
S. A. Kempson ◽  
S. T. Turner ◽  
A. N. Yusufi ◽  
T. P. Dousa
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Pi Transport ◽  
Renal Brush Border Membrane ◽  
Dependent Transport ◽  
Renal Brush Border

Previous studies showed that an increase in NAD+ content in renal cortex in vivo was accompanied by specific inhibition of Na+-dependent inorganic phosphate (Pi) transport across the renal brush border membrane (BBM). Further, in vitro addition of NAD+ to isolated renal BBM vesicles specifically inhibited Na+ gradient-dependent transport of Pi. The present study examined some aspects of the mechanism of this inhibition by NAD+ in vitro and in vivo. When NAD+ was increased in vivo by nicotinamide injection, the apparent Vmax was decreased, but the apparent Km was not different, indicating apparent noncompetitive inhibition. In the presence of 0.3 mM NAD+ added in vitro, the apparent Km for Na+-dependent Pi transport by BBM vesicles was increased, whereas the apparent Vmax was unchanged, indicating apparent competitive inhibition. These changes in apparent Km and apparent Vmax were identical when Pi uptake was measured either at 30-s or at 5-s (the initial rate) incubation times. Inhibition of Pi transport by BBM vesicles in vitro was due primarily to the action of intact added NAD+, although there may be some contribution by isotope dilution due to Pi released from NAD+ by enzymatic hydrolysis. Although in vitro inhibition of Pi transport by added NAD+ was reversed by washing the BBM, the inhibition due to increased NAD+ in vivo persisted after extensive washing of the isolated BBM. The specificity of the inhibitory effect of NAD+ in vivo was indicated by the finding that changes in renal cortical content of ATP or Pi, evoked by loading with glycerol or fructose, did not change BBM transport of Pi.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny of DA1 receptor-mediated natriuresis in the rat: in vivo and in vitro correlations

1992 ◽  
Vol 263 (3) ◽  
pp. R631-R638 ◽  
Author(s):  
S. Kaneko ◽  
F. Albrecht ◽  
L. D. Asico ◽  
G. M. Eisner ◽  
J. E. Robillard ◽  
...  
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Receptor Subtypes ◽  
Renal Brush Border Membrane ◽  
Natriuretic Effect ◽  
Old Rats ◽  
22Na Uptake

The natriuretic and diuretic effects of dopamine are attenuated in the young. Because dopamine has actions on receptors (e.g., adrenergic, serotonin) other than dopamine, we studied a novel dopamine agonist, pramipexole, which has a selectivity to both DA1 and DA2-receptor subtypes. Intravenous administration of pramipexole resulted in a dose-related (1, 10, and 100 micrograms.kg-1.min-1) increase in urine flow and absolute and fractional sodium excretion and a decrease in mean arterial pressure (MAP) in three groups of rats studied. Pramipexole induced a greater decrease in MAP in 6- to 7- (n = 5) and 9- to 16- (n = 6) than in 3- to 4-wk-old (n = 8) rats; the natriuresis and diuresis were greatest in 12- to 16- and least in 3- to 4-wk-old rats. The renal effects of pramipexole were mainly due to actions at the DA1 receptor, since these effects were completely blocked by the coinfusion of a DA1 antagonist, SKF 83742. To explore further a cause of the attenuated natriuretic effect of pramipexole in the young, we studied the effect of a selective DA1-receptor agonist, fenoldopam, on amiloride-sensitive 22Na+ uptake in renal brush-border membrane vesicles. The 3-s amiloride-sensitive uptake was inhibited (45%) by fenoldopam (5 x 10(-5)M) in 9- to 16- (n = 6) but not in 3- to 4-wk-old (n = 5) rats. These studies suggest that the attenuated natriuretic effect of dopamine in the young is in part due to decreased DA1 action on the brush-border membrane Na(+)-H+ exchanger.

Low-affinity transport of pyroglutamyl-histidine in renal brush-border membrane vesicles

1989 ◽  
Vol 257 (5) ◽  
pp. C971-C975 ◽  
Author(s):  
H. A. Skopicki ◽  
K. Fisher ◽  
D. Zikos ◽  
G. Flouret ◽  
D. R. Peterson
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Proximal Tubular Cells ◽  
Tubular Cells ◽  
Luminal Membrane ◽  
Renal Brush Border Membrane ◽  
Proximal Tubular ◽  
Renal Brush Border

These studies were performed to determine if a low-affinity carrier is present in the luminal membrane of proximal tubular cells for the transport of the dipeptide, pyroglutamyl-histidine (pGlu-His). We have previously described the existence of a specific, high-affinity, low-capacity [transport constant (Kt) = 9.3 X 10(-8) M, Vmax = 6.1 X 10(-12) mol.mg-1.min-1] carrier for pGlu-His in renal brush-border membrane vesicles. In the present study, we sought to demonstrate that multiple carriers exist for the transport of a single dipeptide by determining whether a low-affinity carrier also exists for the uptake of pGlu-His. Transport of pGlu-His into brush-border membrane vesicles was saturable over the concentration range of 10(-5)-10(-3) M, yielding a Kt of 6.3 X 10(-5) M and a Vmax of 2.2 X 10(-10) mol.mg-1.min-1. Uptake was inhibited by the dipeptides glycyl-proline, glycyl-sarcosine, and carnosine but not by the tripeptide pyroglutamyl-histidyl-prolinamide. We conclude that 1) pGlu-His is transported across the luminal membrane of the proximal tubule by multiple carriers and 2) the lower affinity carrier, unlike the higher affinity carrier, is nonspecific with respect to other dipeptides.

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