Effect of laser on the remnant liver after the first 24 hours following 70 percent hepatectomy in rats / Efeito do laser no fígado remanescente nas primeiras 24 horas após hepatectomia a 70 por cento em ratos

PURPOSE: To evaluate the mitochondrial function of the remnant liver (RL) in the early phase of liver regeneration in rats after 70 percent partial hepatectomy (PH). METHODS: Sixty male Wistar rats (200-250g) submitted to 70 percent PH were divided into five groups according to the time of euthanasia and application or not of laser light: C = Control, time zero; 2 minutes, 4, 6 and 24 hours after PH. The dose of laser radiation was 22.5 J/cm², wavelength of 660 nm (visible/red), in the remnant liver. We studied the respiration activated by ADP (state 3), basal mitochondrial respiration (state 4), respiratory control ratio (RCR) and mitochondrial membrane potential (MMP). RESULTS: The mitochondrial function of RL changed at 4 and 6 hours after PH, with a significant increase in state 3 and a concomitant increase in state 4 and with maintenance of RCR. MMP differed significantly between the groups biostimulated with laser radiation and the control group 4 hours after HP, with a substantial reduction in the non-laser groups. CONCLUSION: The laser light at the dose used in this study did not induce additional damage to the RL and seems to have delayed the hepatocellular metabolic overload of the remnant liver.

OBJETIVO: Avaliar a função mitocondrial do fígado remanescente (FR) na fase precoce da regeneração hepática em ratos após hepatectomia parcial (HP) a 70 por cento. MÉTODOS: Sessenta ratos machos Wistar (200 - 250g) submetidos à HP a 70 por cento, foram distribuídos em cinco grupos de acordo com o tempo de eutanásia e com aplicação ou não de luz laser: C= Controle,tempo zero; 2 minutos, 4, 6 e 24 horas após HP. O laser foi utilizado na dose 22.5 J/cm², 660 nm, no FR.Estudou-se o estado 3 (respiração ativada por ADP), estado 4 (respiração mitocondrial basal), razão de controle respiratório,estado 3/estado 4 (RCR) e o potencial de membrana mitocondrial(PMM). RESULTADOS: A função mitocondrial do FR alterou-se no período de 4 e 6 horas após a HP com aumento significativo do estado 3 e aumento concomitante do estado 4, com manutenção da RCR. O PMM apresentou diferença significativa entre os grupos bioestimulados com laser e o controle a partir de 4 horas pós HP, com queda importante do grupo sem laser e tendência a equiparação dos valores após 24 horas. CONCLUSÃO: A luz laser, na dose utilizada no presente estudo, não induziu lesão adicional ao FR e parece ter retardado a sobrecarga hepatocelular do fígado remanescente.

Modulation of radiation-induced cytotoxicity in U 87 cells by RH-3 (a preparation of Hippophae rhamnoides).

Background & objectives: Hippophae rhamnoides L. has been widely exploited for medicinal purposes and an extract of its whole berries coded as RH-3 has been found to render radioprotection. Effect of pre-irradiation treatment of up to 10 μg/ml RH-3 was studied in U 87 cells using MTT assay. This study aims at unraveling the mechanism of action of RH-3 in amelioration of radiation-induced cytotoxicity in vitro. Methods: Most effective doses selected were studied further for the elucidation of radiomodifying properties of RH-3, especially with respect to early and late events of apoptosis. Results: RH-3 at concentrations of 7.5 and 10 μg/ml (-15 min) were found most effective in protecting against 2 Gy induced cytotoxicity in terms of MTT reducing ability in U 87 cells. RH-3 was observed to mitigate radiation-induced cellular and mitochondrial free radicals. Mitochondrial membrane potential depletion (studied up to 12 h) was prevented by RH-3 pre-irradiation administration. It could also restore the level of antiapoptotic protein Bcl-2 at 24 and 48 h comparable to the control value. RH-3 also prevented radiation-induced increase in mitochondrial mass at 48 and 72 h post-treatment and the values were comparable to that of control cells. Annexin-V-FITC assay at 12 and 24 h time intervals indicated significant protection against radiation-induced apoptosis by RH-3 pre-irradiation treatment. Interpretation & conclusion: Our findings showed that probably RH-3 acts as an antioxidant preventing cellular and mitochondrial free radical generation that could contribute to its ability to inhibit radiationinduced apoptosis and cytotoxicity.