Expression of nitric oxide and inducible nitric oxide synthase in acute renal allograft rejection in the rat.
BACKGROUND
Recent studies have shown that nitric oxide (NO) synthases, particularly inducible nitric oxide synthase (i-NOS), are induced in acute rejection episodes following heart, liver, pancreas and kidney allotransplantation. Furthermore, tissue and cellular injury has been demonstrated to be mediated by peroxynitrite (ONOO-), a metabolite of NO as well as a potent oxidant. However, a detailed relationship between NO, i-NOS and graft injury in transplantation remains elusive.


METHODS
The present study used the following models of renal transplantation in rats: allografts (n = 5, Brown-Norway to Lewis [LEW] rats), isografts (n = 5, LEW to LEW) and allografts treated with aminoguanidine (AG), an i-NOS inhibitor (n = 5). Blood urea nitrogen (BUN), serum creatinine (SCr) and urinary and serum nitrosocompounds (NOx) were measured on days 2, 4 and 7 post-transplant. Western blot analysis of i-NOS protein expression and measurement of i-NOS activity were carried out in grafts harvested on Day 7, along with immunohistochemical and histopathological examinations.


RESULTS
In the allograft group, both BUN and SCr levels increased markedly on Day 7, in parallel with a sharp increase in NOx. A band stained by anti-i-NOS antibody was detected at approximately 130 kDa, along with high levels of i-NOS activity and diffusely distributed i-NOS-positive cells (macrophages). Histologically, an acute rejection episode was confirmed (Grade 3 according to Banff classifications). In the AG group, reduced renal function and graft injury were significantly less severe than in the allograft group.


CONCLUSIONS
In rat renal allograft acute rejection, markedly increased levels of serum NOx were observed, along with enhanced tissue i-NOS activity, together resulting in graft injury. AG administration suppressed the increase of serum NOx levels, with concomitant mitigation of tissue injury and renal function impairment.
Suzuki
Akio
A
Department of Urology, Hirosaki University School of Medicine, 5 Zaifu-cho, Hirosaki, Aomori 036-8563, Japan.
Kudoh
Shigemasa
S
Mori
Kazuyuki
K
Takahashi
Nobuyoshi
N
Suzuki
Tadashi
T
D000208:Acute Disease; D000818:Animals; D006084:Graft Rejection / Q000378:metabolism*; D016030:Kidney Transplantation; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis*; D051381:Rats; D011914:Rats, Inbred BN
D009569:Nitric Oxide; D019001:Nitric Oxide Synthase