Age-related differences in function and structure of rat livers subjected to ischemia/reperfusion.

INTRODUCTION: Liver function is affected during ischemia/reperfusion (IR). The current state of knowledge about liver aging processes during IR is incomplete. We evaluated the effects of aging on liver structure and function under IR conditions. MATERIAL AND METHODS: Animals were divided into control (C-2) and ischemia/reperfusion (IR-2) groups of young rats (2-4 months old) and C-12 and IR-12 groups of old rats (12-14 months old). The livers from IR-2 and IR-12 groups were subjected to partial ischemia (60 min), followed by global reperfusion (4 h). Blood samples were obtained during reperfusion (0, 30 and 240 min) to estimate the activity of aminotransferases (ALT, AST). After IR, tumor necrosis factor-α (TNF-α), interleukin-1b (IL-1b), malondialdehyde (MDA), and superoxide dismutase (SOD) were determined in liver homogenates. RESULTS: At all points of reperfusion, an increase in aminotransferase activity levels in the ischemic groups was observed; mainly between IR-12 and C-12 rats. The concentration of TNF-α was significantly higher in young animals (in non-ischemic groups: p = 0.09, in ischemic groups: p = 0.05). Under IR conditions, the concentration of IL-1b dropped (p = 0.05). The concentration of MDA was significantly higher in mature animals (in non-ischemic groups: p = 0.09, in ischemic groups: p = 0.05). In ischemic groups an increase in necrosis rate was observed regardless of age. Rats in the IR-12 group showed the most pronounced changes in hepatic architecture, including increased micro- and macrosteatosis and parenchymal cell destruction. CONCLUSIONS: The function and structure of mature livers slightly deteriorate with age and these differences are more noticeable under IR conditions.

The influence of bexarotene, a selective agonist of the retinoid receptor X (RXR), and tazarotene, a selective agonist of the retinoid acid receptor (RAR), on bone metabolism in rats.

PURPOSE: The purpose of this study was to investigate the influence of selective agonists of the retinoid receptor X (RXR) and the retinoid acid receptor (RAR) on bone metabolism in rats. METHODS: Thirty six male Wistar rats were divided into three groups: receiving bexarotene, or tazarotene, or to control group. Serum biochemical markers of bone turnover (osteocalcin - OC, tartrate resistant acid phosphatase 5 - TRACP5b and osteoprotegerin - OPG) and mechanical properties of bones were analyzed. RESULTS: There was a significant decrease in the femur index value in groups receiving tazarotene and bexarotene on Day 14 (8% and 20% respectively, p=0.0039). On Day 28, 14 days after discontinuation of tazarotene and bexarotene, the difference in femur indexes was still significant (4% for T1-6 and B1-6, p=0.0270). In the bexarotene group an increase in mean plasma osteocalcin level and mean plasma TRACP5b level was detected. In the tazarotene group the mean osteocalcin level remained unchanged and the mean plasma TRACP5b level decreased. An increased yield stress was detected in groups receiving retinoids comparing to controls after 14 days of tazarotene and bexarotene administration. CONCLUSION: Although bexarotene and tazarotene administration caused decrease in the femur index, mechanisms responsible for that effect seem to be different. Our results suggest that bexaroten increases bone turnover. On the contrary, tazaroten seems to have inhibitory effect on bone turnover. A counter influence of selective RAR and RXR agonists on the bone turnover might be the reason for inconsistency in results from published research concerning the influence of retinoids on bone metabolism.

The impact of morin, a natural flavonoid, on cyclophosphamide-induced changes in the oxidative stress parameters in rat livers.

BACKGROUND: Cyclophosphamide (CPX) has many adverse effects, partly due to oxidative stress induction in various tissues. Morin is one of the natural flavonoids with strong antioxidant properties. OBJECTIVES: The aim of the current research was to estimate the influence of morin on changes in antioxidant parameters in rat livers after cyclophosphamide administration. MATERIAL AND METHODS: The study was performed on Wistar rats. The rats in Group C received 0.9% saline; those in Group CX received cyclophosphamide (CPX); and those in Group M-CX received CPX with morin. Cyclophosphamide and morin were given by gastric gavage for 10 consecutive days at doses of 15 mg/kg and 100 mg/kg, respectively. Malondialdehyde (MDA) and glutathione (GSH) concentrations, superoxide dismutase (SOD) activity and catalase (CAT) activity were determined in liver tissue homogenates. RESULTS: CPX caused a significant decrease in SOD activity and GSH levels, but only the latter was fully restored by morin. There were no significant differences in CAT activity in the various groups. CPX also insignificantly decreased MDA levels, which was aggravated by co-administration of morin. CONCLUSIONS: The results obtained indicate that morin may exert some protective action on CPX-induced changes in the antioxidant state in rat livers.

Age-related changes in ADMA-DDAH-NO pathway in rat liver subjected to partial ischemia followed by global reperfusion.

BACKGROUND: Liver function is affected during ischemia/reperfusion (IR). We evaluated the effect of the aging process on selected parameters determining the NO level in rat liver subjected to IR. METHODS: The animals were divided into the C-2 and the IR-2 group of young rats (2-4 months old) and the C-12 and the IR-12 group of older rats (12-14 months old). Livers belonging to the IR-2 and the IR-12 group were subjected to partial ischemia (60 min) and reperfusion (4 h). Blood samples were obtained after surgeries to estimate the activity of aminotransferases, as well as just before ischemia and during reperfusion (15, 120, and 240 min) to estimate concentration of arginine (Arg) and its derivatives: asymmetric and symmetric dimethylarginine (ADMA, SDMA). After IR, dimethylarginine dimethylaminohydrolase (DDAH) activity and protein concentration of inducible nitric oxide synthase (iNOS) were measured in liver homogenates. RESULTS: In the IR-2 group ADMA level increased the most between 15 and 120 min of reperfusion and was the highest of all the groups (0.72±0.2 µmol/l). In the IR-12 group ADMA level decreased significantly and was lower compared to all the other groups at 15 min (0.42±0.2 µmol/l) and to IR-2 at 120 (0.52±0.1 µmol/l) and 240 min (0.38±0.1 µmol/l) of reperfusion. Only the IR-2 group SDMA level increased significantly between 15 (0.75±0.9 µmol/l) and 240 min (1.0±1.2 µmol/l) of reperfusion. At the beginning of the surgery the Arg level was significantly higher in young rats (C-2: 102.1±35.7 µmol/l; IR-2: 114.63±28.9 µmol/l) than in older ones (C-12: 41.88±44.7 µmol/l; IR-12: 28.64±30.6 µmol/l). In the C-2 group the Arg level (77.41±37.5 µmol/l) and Arg/ADMA (A/A) ratio (138.03±62.8 µmol/l) were significantly higher compared to the ischemic groups at 15 min and to all the other groups at 120 (Arg: 47.17±31.7 µmol/l; A/A: 88.28±66.2 µmol/l) and 240 min (Arg: 43.87±21.9 µmol/l; A/A: 118.02±106.3 µmol/l). In the IR-2 group Arg level (11.4±12.0 µmol/l) and A/A ratio (16.11±16.2 µmol/l) decreased significantly at 15 min and during the next phase of reperfusion the levels of those parameters were low, comparably to those in IR-12. As a result of IR, a decrease in DDAH activity and an increase in iNOS protein concentration were observed only in the young rats. CONCLUSIONS: We found that in the non-ischemic groups the Arg level may be affected by the aging process. Under IR conditions, important changes in DDAH-ADMA-NO pathway were observed only in young livers.

Influence of ezetimibe on ADMA-DDAH-NO pathway in rat liver subjected to partial ischemia followed by global reperfusion.

BACKGROUND: We evaluated effect of ezetimibe on selected parameters determining NO level in rat liver subjected to ischemia reperfusion (IR). METHODS: Rats received ezetimibe (5 mg/kg) (groups E0 and EIR) or saline solution (groups C0 and CIR) intragastrically for 21 days. Then, the livers of CIR and EIR underwent ischemia (60 min) and reperfusion (4 h). Blood samples were obtained before surgery to estimate activities of aminotransferases, and just before ischemia and during reperfusion to estimate asymmetric and symmetric dimethylarginine (ADMA, SDMA) and arginine (Arg) levels. After IR, dimethylarginine dimethylaminohydrolase (DDAH) activity and endothelial nitric oxide synthase (eNOS) protein concentration were measured in liver homogenates. DDAH and protein arginine methyltransferase (PRMT) mRNA were quantified by real-time PCR in liver tissue samples. RESULTS: In CIR, the ADMA level was significantly higher compared to all other groups in 30 min and to E0 group in 120 min of reperfusion. In EIR, ADMA was low, compared to non-ischemic groups. At 30 and 120 min of reperfusion, in non-ischemic groups the level of Arg and Arg/ADMA ratio were significantly higher than in ischemic groups and E0 was the group with the highest levels of those parameters of all. In CIR, eNOS protein concentration was significantly lower than in ezetimibe-treated groups. Activity of DDAH was significantly higher in E0 than in non-treated groups. In ischemic groups, DDAH mRNA expression was significantly higher than in non-ischemic ones and PRMT mRNA expression was significantly higher in C0 than in all other groups. CONCLUSIONS: Influence of ezetimibe on ADMA/DDAH/NO pathway demonstrated in this work may suggest protective properties of this drug on rat livers injured by IR and, to a lower extent, on livers non-subjected to IR.

Effect of cyclophosphamide and morin-5'-sulfonic acid sodium salt, alone or in combination, on ADMA/DDAH pathway in rats.

BACKGROUND: The aim of the study was to evaluate the effect of cyclophosphamide (CPX) and morin-5'-sulfonic acid sodium salt (NaMSA) on plasma asymmetric dimethylarginine (ADMA) level and dimethylarginine dimethylaminohydrolase (DDAH) activity in rat liver. METHODS: The study was performed on Wistar rats receiving normal saline, CPX (15 mg/kg/day), NaMSA (100 mg/kg/day) or both CPX and NaMSA for 10 consecutive days. RESULTS: Significant decrease in ADMA level was found in all groups when compared to the control. DDAH activity in the liver was significantly higher in CX group compared to the control group. CONCLUSION: Obtained results of ADMA/DDAH pathway parameters require further research.