Gender differences in hepatic ischemic reperfusion injury in rats are associated with endothelial cell nitric oxide synthase-derived nitric oxide.
OBJECTIVE
This study was designed to examine the hypothesis that gender differences in I/R injury are associated with endothelial cell nitric oxide synthase (eNOS)-derived nitric oxide (NO).


METHODS
Wistar rats were randomized into seven experimental groups (12 animals per group). Except for the sham operated groups, all rats were subjected to total liver ischemia for 40 min followed by reperfusion. All experimental groups received different treatments 45 min before the laparotomy. For each group, half of the animals (six) were used to investigate the survival; blood samples and liver tissues were obtained in the remaining six animals after 3 h of reperfusion to assess serum NO, alanine aminotransferase (ALT) and TNF-alpha levels, liver tissue malondialdehyde (MDA) content, and severity of hepatic I/R injury.


RESULTS
Basal serum NO levels in female sham operated (FS) group were nearly 1.5-fold of male sham operated (MS) group (66.7+/-11.0 micromol/L vs 45.3+/-10.1 micromol/L, P<0.01). Although serum NO levels decreased significantly after hepatic I/R (P<0.01, vs sham operated groups), they were still significantly higher in female rat (F) group than in male rat (M) group (47.8+/-8.6 micromol/L vs 23.8+/-4.7 micromol/L, P<0.01). Serum ALT and TNF-alpha levels, and liver tissue MDA content were significantly lower in F group than in M group (370.5+/-46.4 U/L, 0.99+/-0.11 microg/L and 0.57+/-0.10 micromol/g vs 668.7+/-78.7 U/L, 1.71+/-0.18 microg/L and 0.86+/-0.11 micromol/g, respectively, P<0.01). I/R induced significant injury to the liver both in M and F groups (P<0.01 vs sham operated groups). But the degree of hepatocyte injury was significantly milder in F group than in M group (P<0.05 and P<0.01). The median survival time was six days in F group and one day in M group. The overall survival rate was significantly higher in F group than in M group (P<0.05). When compared with male rats pretreated with saline (M group), pretreatment of male rats with 17-beta-estradiol (E2) (M+E2 group) significantly increased serum NO levels and significantly decreased serum ALT and TNF-alpha levels, and liver tissue MDA content after I/R (P<0.01). The degree of hepatocyte injury was significantly decreased and the overall survival rate was significantly improved in M+E2 group than in M group (P<0.01 and P<0.05). The NOS inhibitor N(w) -nitro-L-arginine methyl ester (L-NAME) treatment could completely abolish the protective effects of estrogen in both male and female rats.


CONCLUSIONS
The protective effects afforded to female rats subjected to hepatic I/R are associated with eNOS-derived NO.
Lü
Ping
P
Department of General Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, China. luliu@public.wh.hb.cn
Liu
Fang
F
Wang
Chun-You
CY
Chen
Dao-Da
DD
Yao
Zhong
Z
Tian
Yuan
Y
Zhang
Jing-Hui
JH
Wu
Yi-Hua
YH
D000818:Animals; D042783:Endothelial Cells / Q000201:enzymology; D005260:Female; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000378:metabolism*; D012727:Sex Characteristics
D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat