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

Abstract

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.

Keywords: ageing; inflammation; ischemia/reperfusion; liver; oxidative stress; rat.

Figure 1

The effect of IR and aging on ALT (A) and AST (B) activity The values are presented as mean ± SD. C-2 – young rats non-subjected to IR, C-12 – mature rats not subjected to IR, IR-2 – young rats subjected to IR, IR-12 – mature rats subjected to IR; *p < 0.05 and ***p < 0.005 (IR-12 vs. C-12), ^#p < 0.05 (IR-2 vs. C-2), ^∆∆∆p < 0.005 (IR-12 vs. IR-2).

Figure 2

The effect of IR and aging on cytokine (TNF-α (A) and IL-1b (B)) levels The values are presented as mean ± SD. C-2 – young rats non-subjected to IR, C-12 – mature rats not-subjected to IR, IR-2 – young rats subjected to IR, IR-12 – mature rats subjected to IR; ^∆∆∆ p < 0.005 (IR-12 vs. IR-2), ^ΦΦp < 0.01 and ^ΦΦΦp < 0.005 (C-12 vs. C-2).

Figure 3

The effect of IR and aging on the activity of SOD (A) and the concentration of MDA (B) The values are presented as mean ± SD. C-2 – young rats non-subjected to IR, C-12 – mature rats not-subjected to IR, IR-2 – young rats subjected to IR, IR-12 – mature rats subjected to IR; ^∆∆p < 0.01 (IR-12 vs. IR-2), ^ΦΦp < 0.01 (C-12 vs. C-2).

Figure 4

Histopathological examination of liver tissue (stained with hematoxylin-eosin) from group C-2 – young rats non-subjected to IR (A), group IR-2 – young rats subjected to IR (B), group C-12 – mature rats not subjected to IR (C), and from group IR-12 – mature rats subjected to IR (D). Livers from C-2 and C-12 groups featured normal architecture and only low degree of steatosis, but from IR-2 and IR-12 groups presented higher rate of the necrosis associated with intense neutrophil infiltrate