EFFECTS OF CALCIUM-CHANNEL BLOCKER ON GENE-EXPRESSION OF C-FOS AND EGF AFTER ISCHEMIC RENAL INJURY

초록

Acute ischemic renal failure is an important clinical entity with increasing tendency, with a permanent loss of renal function frequently being observed. Recent work has demonstrated that growth factors play a significant role in mediating theregeneration process leading to recovery from acute renal failure. The effect of calcium channel blocker on gene expression after ischemic renal injury was studied. In these studies, experimental animals were dividedinto four groups: Group I (N = 3) was the control without any procedure; Group II (N = 3) was the sham operation group (bilateral flank incisionand decapsulation were done without renal artery clamping); Group III (N= 15) was the ischemic renal injury model by right nephrectomy and left renal artery clamping for 40 minutes; Group IV (N = 15)was the ischemic renal injury group with nifedipine pretreatment (10 mg/kg, s.c.). In the ischemic renal failure model (Groups III and IV), rats were further divided into three subgroups according to reperfusion time, such as 1, 24, and 72 hours. Total renal RNA was purified by the Chomczynski method. After the isolation of RNA, electrophoresis was done in a 1% agarose gel containing 2.2 M formaldehyde, and confirmation of intact RNA was done by the 18S and 28S ribosomal RNA band. RNA transfer was done byvacuum transfer system and then the hybridization was performed at 42°Cwith isotope labeled probes for 24 hours. Autoradiographs were obtained and quantitated by densitometer at 530 nm. The following results were obtained, and the changes of serum creatinine were as follows: in the control group 0.9 0.2 mg/dl; in the sham operation group 0.8 0.3 mg/dl; in the ischemic group without nifedipine pretreatment according to reperfusion time, respectively 0.9 0.3 mg/dl (1 hr), 1.9 0.5 mg/dl (24 hrs), and 3.6 1.4 mg/dl (72 hrs); in the ischemic group with nifedipine pretreatment according to reperfusion time, respectively 0.5 0.1 mg/dl, 2.4 1.2 mg/dl, and 3.5 2.5 mg/dl. The mean serum creatinine level was statistically significant between the control and post-ischemic 24, 72 hours reperfusion groups (P < 0.05). c-fos gene expression was rapidly increased by renal ischemia with the peak after 60 minutes of reperfusion and then it rapidly decreased. EGF gene expression was rapidly decreased after the renal ischemia and slowly recovered in activity after 72 hours of reperfusion. Gene expression pattern of ischemic renal injury with nifedipine pretreatment was similar to the ischemic group without nifedipine pretreatment. From the above findings, c-fos and EGF gene expression are probably important in the recovery of ischemic renal injury. However, calcium channel blocker did not influence the gene expression of c-fos and EGF after ischemic renal injury.