Background. Acute renal failure (ARF) is defined as an abrupt decrease of glomerular filtration rate that is accompanied by an accumulation of nitrogenous waste products. Since tubular cell injury is the hallmark of ischemic ARF, an understanding
of the
mechanisms of ischemic cellular damage and dysfunction is essential to limit and possibly to prevent ischemic injury. Various pathophysiologic changes such as cellular ATP depletion, intracellular calcium alterations, mitochondrial dysfunction,
oxygen
free radical formation or renin-angiotensin system are proposed to be involved in the mechanism of ARF. Of these changes, the formation of reactive oxygen species in the reperfusion period and alteration of renin-angiotensin system have been
suggested
as a mediator of tubular cell injury and abnormal renal hemodynamics. So to investigate the expression of antioxidant superoxide dismutase (SOD) and renin genes during acute ischemic renal injury, the author performed the northern and dot
hybridization
of renal tissue at different reperfusion time in the ischemic ARF rats.
Methods. In this experiment, 21 rats were divided into three groups ; Group I (n=3) was a control group ; Group I (n=3) was a control group without any procedure, group II (n=3) was a sham operation group with bilateral flank incision and
decapsulation
of the kidneys Group III(n=15) was an ischemic model with right nephrectomy followed by left renal artery clamping for 40minutes. In the ischemic renal injury group (Group III), the rats were subdvided into three subgroups according to the
reperfusion
time such as 1, 24, and 72 hours (Group IIIa, IIIb, IIIc respectively). In all cases, whole blood was collected for the measurement of serum creatinine after each reperfusion time. And total renal RNA was purified by Chomczynski method after each
reperfusion time. After the isolation of RNA, electrophoresis was done in a 1% agarose gel containing 2.2M formaldehyde, and confirmation of intact RNA were done by the 18S ribosomal RNA transfer was done by vaccum transfer system and then
hybridization
was performed at 42℃ with isotope labelled probes for 18 hours. Autoradiographs were obtained and quantitated by computer assisted dual wave length flying spot scanner (CS-9000) at 530nm.
Results. The mean levels of serum creatintne were as follows: in the control group, 0.9±0.3mg/dl; in the ischemic group after 24 hours reperfusion, 1.9±0.5mg/dl and in the ischemic group after 72hours reperfusion, 3.6±1.4mg/dl. The difference
of
mean
serum creatinine levels between control and post-ischemic 24 and 72 hours reperfusion groups was statistically significant (P<0.05).
SOD gene expression was markedly decreased by renal ischemia and showed persistently decreased pattern during reperfusion period. The expression of renin gene was markedly decreased after on ehour of reflow and progressively increased to one half
of the
control level 72 hours after reperfusion.
Conclusion. From the above findings, SOD gene expression was rapidly decreased after ischemia and this antioxidant enzyme probably does not act as a protective mechanism of acute ischemic renal failure. Expression pattern of renin gene suggest
that
renin gene is not expressed as a direct mediator of acute ischemic renal injury but probably has some roles in the recovery phase of ARF. Although the specific role of SOD and renin genes are still not known in ischemic renal injury, more studies
including in sity hybridization will be requested in the future.
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