Effects of N-acetylcysteine and Methylprednisolone on Lung Injury in a Paraquat-Poisoned Rat Model

BACKGROUND: This study evaluated the inhibitory effects of N-acetylcysteine(NAC) and methylprednisolone on lung injury in the paraquat-poisoned rat model. METHODS: Sixty rats were divided into four groups(n=15 in each group) accordingly to the drug administered : group I, only intraperitoneally injected paraquat (20 mg/kg); group II, intraperitoneally injected paraquat and NAC(300 mg/kg); group III, intraperitoneally injected paraquat and methylprednisolone(60 mg/kg); and group IV, intraperitoneally injected paraquat, NAC(300 mg/kg), and methylprednisolone(60 mg/kg). On the 7th day after injection, the survival rate of experimental rats and the positive area of collagen fiber in the injured lung stained by Masson's trichrome were evaluated. RESULTS: 1. There were no differences in the 7-day survival rates for the four groups. 2. The percent of collagen fiber for group II(6.3+/-4.7%) was significantly decreased in comparison with that for group I (14.4+/-9.7%). 3. The percent of collagen fiber for Group III(13.2+/-5.9%) was not significantly different from that for group I(14.4+/-9.7%). 4. The percent of collagen fiber for Group IV(6.9+/-4.6%) was significantly decreased in comparison with that for group I, but was not different from that for group II. CONCLUSION: These results suggest that NAC protects against pulmonary fibrosis in paraquat-poisoned rats whereas methylprednisolone does not protect against pulmonary fibrosis.

Effect of Pentoxifylline on the Cerebral No-reflow Phenomenon after Cardiac Arrest in Rat

BACKGROUND: Successful resuscitation of the brain requires unimpaired blood recirculation. However, unfortunately there are several factors against the successful recirculation. No-reflow phenomenon, characterized by a lack of reperfusion after cerebral ischemia, is the most important pathogenic factor during the early period of spontaneous circulation(ROSC). This study addresses question that pentoxifylline(PTX) ameliorates no-reflow phenomenon after cardiac arrest. METHODS: Fourteen rats were divided three group ; Sham group(n=2), 12 minutes cardiac arrest group without PTX(group I, n=6), and 12 minutes cardiac arrest group pretreated with PTX(group II, n=6). Group II were premedicated by intravascular injection of 5mg/kg PTX into the external jugular vein before 5minutes of the arrest-induction. We induced cardiac arrest with endotracheal clamping and muscle relaxant. And then, resuscitation was initiated. Arterial blood samples were drawn at the femoral artery before 5 minutes of arrest-induction and at the 5 minutes after restoration of ROSC. Reperfusion of brain was visualized by injection of 0.3g/kg of 15% FITC-albumin at 5 minutes after restoration of ROSC, and the animals were decapitated 2 minutes later. The left hemisphere was fixed with 4% formalin, and coronal sections of 200um thickness at three different standard levels of the rat brain were investigated with fluorescence microscopy. Density of microvasular filling were identified and calculated. RESULTS: Our observation demonstrated that 1. There were no significant differences of blood pressures, heart rates, and results of blood gas analysis between group I and II during the prearrest steady state. 2. There were no significant differences of blood pressures, heart rates, and results of blood gas analysis between group Iand II at 5minutes after ROSC. 3. Group II premedicated with PTX, showed significant increased capillary refiling(0.310+/-0.035)than group I without PTX(0.181+/-0.040). CONCLUSIONS : The results showed that during the prearrest steady state, premedication of PTX ameliorated the no-reflow phenomenon in the rat model of the asphyxial arrest. Further experimental studies are required to focus on the effects of postarrest infused PTX, The neurologic outcome, and the clinical applications.