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Nitric oxide synthase activity in renal ischemia-reperfusion injury in the rat: implications for renal
D A Shoskes1, Y Xie, N F Gonzalez-Cadavid
1Department of Surgery, Harbor-UCLA Medical Center, UCLA School of Medicine, Torrance, California 90509, USA.
Abstract:
Cadaveric kidney transplants with delayed graft function have poorer graft survival by an unknown mechanism. Nitric oxide, produced by nitric oxide synthase (NOS), has a proven role in both recovery of ischemia and promotion of rejection. We therefore wished to study the patterns of NOS activity in a model of renal ischemia. The left renal pedicle of Fisher rats was occluded for 1 hr. Both kidneys were removed at various times and frozen. Renal NOS activity was measured by conversion of [3H]arginine to [3H]citrulline and the content of endothelial NOS isoenzyme (eNOS) was compared by Western blot. NOS activity increased significantly in the left ischemic kidney over the first 24 hr, from a control of 33.8 pmol/min/mg to 79.8 at 2 hr and 56.8 at 24 hr. NOS activity then dropped below baseline, returning to near normal levels at day 21. eNOS content was stimulated over the entire time course, consistent with the presence of an eNOS inhibitor. Oral treatment with the NOS substrate L-arginine at 5 g/L significantly hastened the return of serum creatinine to baseline, if simultaneous contralateral nephrectomy was performed. The lazaroid U74389G given perioperatively also improved renal function and hastened recovery of NOS activity. Because nitric oxide plays an important role in maintaining blood flow during recovery from renal ischemia, the observed decrease in NOS activity may be prevented by perioperative treatment with oral L-arginine and corticosteroids. In addition, U74389G may provide a clinically useful method of minimizing and/or shortening DGF, thereby improving graft function and survival.
Insights
Nitric oxide synthase (NOS) activity initially rises then falls after kidney ischemia. L-arginine and U74389G treatments improved kidney function and hastened NOS recovery, potentially reducing delayed graft function in transplants.
Area of Science:
- Nephrology
- Transplantation Immunology
- Biochemistry
Background:
- Delayed graft function (DGF) in cadaveric kidney transplants is linked to poorer outcomes via unknown mechanisms.
- Nitric oxide (NO), synthesized by nitric oxide synthase (NOS), influences both ischemic recovery and transplant rejection.
- Understanding NOS activity patterns in renal ischemia is crucial for improving transplant success.
Purpose of the Study:
- To investigate the temporal changes in nitric oxide synthase (NOS) activity and endothelial NOS (eNOS) content following renal ischemia in a rat model.
- To evaluate the therapeutic potential of L-arginine and the lazaroid U74389G in mitigating the effects of renal ischemia and improving graft function.
Main Methods:
- Renal ischemia was induced in Fisher rats by 1-hour occlusion of the left renal pedicle.
- Renal NOS activity was quantified using [3H]arginine to [3H]citrulline conversion assays.
- Endothelial NOS (eNOS) content was assessed via Western blot analysis.
- Intervention groups received oral L-arginine or perioperative U74389G.
Main Results:
- NOS activity significantly increased in the ischemic kidney within 24 hours, then decreased below baseline levels.
- eNOS content remained elevated throughout the study period, suggesting the presence of an eNOS inhibitor.
- L-arginine administration accelerated serum creatinine normalization in rats undergoing contralateral nephrectomy.
- U74389G treatment improved renal function and expedited NOS activity recovery.
Conclusions:
- The observed decrease in NOS activity post-ischemia may be a key factor in poorer graft survival.
- Perioperative L-arginine and corticosteroids could potentially prevent this NOS decrease.
- U74389G shows promise in minimizing and shortening DGF, thereby enhancing kidney transplant graft function and survival.