Ed. Kharasch et al., ROLE OF RENAL CYSTEINE CONJUGATE BETA-LYASE IN THE MECHANISM OF COMPOUND-A NEPHROTOXICITY IN RATS, Anesthesiology, 86(1), 1997, pp. 160-171
Background: The sevoflurane degradation product compound A is nephroto
xic in rats, in which it undergoes extensive metabolism to glutathione
and cysteine S-conjugates. The mechanism of compound A nephrotoxicity
in rats is unknown. Compound A nephrotoxicity has not been observed i
n humans. The authors tested the hypothesis that renal uptake of compo
und A S-conjugates and metabolism by renal cysteine conjugate beta-lya
se mediate compound A nephrotoxicity in rats. Methods: Compound A (0-0
.3 mmol/kg in initial dose-response experiments and 0.2 mmol/kg in sub
sequent inhibitor experiments) was administered to Fischer 344 rats by
intraperitoneal injection. Inhibitor experiments consisted of three g
roups: inhibitor (control), compound A, or inhibitor plus compound A.
The inhibitors were probenecid (0.5 mmol/kg, repeated 10 h later), an
inhibitor of renal organic anion transport and S-conjugate uptake; aci
vicin (10 mg/kg and 5 mg/kg 10 h later), an inhibitor of gamma-glutamy
l transferase, an enzyme that cleaves glutathione conjugates to cystei
ne conjugates; and aminooxyacetic acid (0.5 mmol/kg and 0.25 mmol/kg 1
0 h later), an inhibitor of renal cysteine conjugate beta-lyase, Urine
was collected for 24 h and then the animals were killed, Nephrotoxici
ty was assessed by light microscopic examination and biochemical marke
rs (serum urea nitrogen and creatinine concentration, urine volume and
urine excretion of protein, glucose, and alpha-glutathione-S-transfer
ase [(alpha GST], a marker of tubular necrosis). Results: Compound A c
aused dose-related nephrotoxicity, as shown by selective proximal tubu
lar cell necrosis at the corticomedullary junction, diuresis, proteinu
ria, glucosuria, and increased alpha GST excretion. Probenecid pretrea
tment significantly (P < 0.05) diminished compound A-induced increases
(mean +/- SE) in urine excretion of protein (45.5 +/- 3.8 mg/24 h vs.
25.9 +/- 1.7 mg/24 h), glucose (28.8 +/- 6.2 mg/24 h vs. 10.9 +/- 3.2
mg/24 h), and alpha GST (6.3 +/- 0.8 mu g/24 h vs. 1.0 +/- 0.2 mu g/2
4 h) and completely prevented proximal tubular cell necrosis, Aminooxy
acetic acid pretreatment significantly diminished compound A-induced i
ncreases in urine volume (19.7 +/- 3.5 ml/24 h vs. 9.8 +/- 0.8 ml/24 h
), protein excretion (37.2 +/- 2.7 mg/24 h vs. 22.2 +/- 1.8 mg/24 h),
and alpha GST excretion (5.8 +/- 1.5 vs. 2.3 mu g/24 h +/- 0.8 mu g/24
h) but did not significantly alter the histologic pattern of injury,
In contrast, acivicin pretreatment increased the compound A-induced hi
stologic and biochemical markers of injury. Compound A-related increas
es in urine fluoride excretion, reflecting compound A metabolism, were
not substantially altered by any of the inhibitor treatments, Conclus
ions: Intraperitoneal compound A administration provides a satisfactor
y model of nephrotoxicity, Aminooxyacetic acid and probenecid signific
antly diminished histologic and biochemical evidence of compound A nep
hrotoxicity, whereas acivicin potentiated toxicity. These results sugg
est that renal uptake of compound A-glutathione or compound A-cysteine
conjugates and cysteine conjugates metabolism by renal beta-lyase med
iate, in part, compound A nephrotoxicity in rats.