| Many studies showed that high-altitude hypoxia affected expressions and metabolic activities of drug-metabolizing enzymes.The altereted expressions and activities of drug-metabolizing enzymes might affect pharmacokinetics and efficacies of drugs.Recognized factors for effects of hypobaric hypoxia on drug metabolism enzymes are rate of ascent,altitude attained,duration of high-altitude exposure.We studied the effects of acute and chronic hypoxia on drug metabolizing enzymes in rats.Many researches stuided on the effects of hypoxia on drug metabolizing enzymes,but they mainly focus on CYP450 and most of them are about acute hypoxia.There are relatively few studies on the effects of chronic hypoxia on CYP450 and phase II metabolizing enzymes.The study of the effects of acute and chronic hypoxia on drug metabolism enzymes is significant for promoting rational drug use at high altitudes.The present study mainly includes the following parts:In the first part,we studied the effects of acute and chronic hypoxia on the arterial blood gas,vein biochemistry,and liver pathology in rats.The degree of hypoxic injury in rats was evaluated.Blood gas results showed that the Pa O2,Sa O2,p H,TCO2,and HCO3-were significantly decreased in rats after acute and chronic hypoxic exposure,indicating that the blood oxygen saturation of rats decreased,the supply of oxygen was imbalanced,and the acid-base imbalance was observed.Acute hypoxia 24 h,Pa O2 and Sa O2 decreased the most significant.Compared with the control group,the ALT and AST of rats in the acute hypoxia increased more than that in the chronic hypoxia 7 d,indicating that the acute hypoxic liver injury was more severe than the chronic hypoxia 7d.Pathological analysis showed that edema and inflammatory infiltration of hepatocytes occurred after hypoxia in rats.It was further proved that liver tissue damage was caused by hypoxia.The results showed that rats were hypoxic after acute and chronic hypoxia,and liver damage occurred in rats.In the second part,the effects of acute and chronic hypoxia on the activity and the expression of CYP450 were studied.We used the "Cocktail" probe drug method in combination with liver microsome in vitro incubation assay to measure CYP450 activity.A UPLC method was established to simultaneously determine the activities of five CYP450 subtypes.The experimental results showed that both acute and chronic hypoxia decreased the activity and protein expression of CYP1A2,and the activity decreased significantly in chronic hypoxia,while the protein expression changed most significantly at 12 h after acute hypoxia;In acute hypoxia,the activity of CYP3A4 did not change and the protein expression was significantly reduced.When CYP3A4 activity was increased during slow hypoxia,protein expression was almost unchanged at this time;acute hypoxia did not affect activity of CYP2C9,chronic hypoxia increased activity of CYP2C9,acute and chronic hypoxia did not affect CYP2C9 protein expression;activity and protein expression of CYP2C9 were elevated at 24 h acute hypoxia,chronic hypoxia did not change;The activity of CYP2E1 did not change during acute hypoxia.The activity of chronic hypoxia decreased at 7 days,while the protein expression decreased at 12 hours after acute hypoxia.Chronic hypoxia 7d did not affect the protein expression of CYP2E1.The results showed that hypoxia affects the activity and protein expression of CYP450,and the effects of acute and chronic on CYP450 are different.In the use of plateau hypoxia on the impact of CYP450 to guide the plateau medication to take into account the time factor.In the third part,we studied the effects of acute and chronic hypoxia on the activity and protein expression of rat II phase metabolizing enzymes UGT1A1 and UGT1A6.The same study we used probe drug method in combination with liver microsomal in vitro incubation to detect the activities of UGT1A1 and UGT1A6.A UPLC method was established for the determination of p-nitrophenol by the UGT1A1 probe drug β-estradiol and the UGT1A6 probe.Western blot was used to measure the protein expressiones of UGT1A1 and UGT1A6.The experimental results showed that compared with the control group,acute and chronic hypoxia did not affect the activity of UGT1A1 in rat.UGT1A6 activity was changed by 35.77%,63.90% respectively after acute hypoxia 24 h and chronic hypoxia 7d(P<0.01).UGT1A6 protein expression was decreased in both acute and chronic hypoxia,while protein expression was most significantly reduced at after acute hypoxia of 12 h.Acute and chronic hypoxia affect the activity and protein expression of UGT1A1 and UGT1A6,which may affect the pharmacokinetics of the drugs they metabolize.In the fourth part,we studied the effects of the plateau and plateau on the differences of CYP450 activity and protein expression in rats.The experimental results showed that the trends of activity of CYP450 in the field and the simulated group were basically the same.There was no significant difference in the protein expression of CYP1A2 between the simulated group and the correspond-field group;acute hypoxia reduced the protein expression of CYP3A4,and the simulated group decreased much more than the corresponding field group.The expression of CYP3A4 protein in the simulated group decreased after chronic hypoxia for 7 days.However,there was no change in the protein expression of CYP3A4 in the hypoxia 7d group,and there was a significantly difference between the hypoxia 24 h mock and field groups of CYP2C19.Compared with the control group,the protein expression in the hypoxia 24 h group increased,but the field deficiency and the expression of protein in the 24 h oxygen group was unchanged;the protein expression in the CYP2E1 mimic hypoxia 12 h group was increased,while the change in the hypoxia 12 h group was not observed.The effect of simulated plateau and plateau on CYP450 is not completely the same.We must study the effect of high altitude hypoxia on drug metabolizing enzymes.In the fifth part,the effects of hypoxia and hypoxic rat serum on the expressiones of CY1A2 and CYP2E1 proteins in hepatocytes of rat were studied.The results showed that hypoxia did not change the protein expression of CY1A2 in rat hepatocytes,and the serum of hypoxic 7 d rats reduced the protein expression of CY1A2 in normoxic hepatocytes.The hypoxic 12 h and 24 h rat serum also reduced the protein expression of CY1A2 in hypoxic hepatocytes.Hypoxia reduced the expression of CYP2E1 protein,and the expression of CYP2E1 protein in hepatocytes in hypoxia 7 d rat serum was further decreased.Hypoxia rat serum cultured in hypoxia 12 h,24 h,7d rats had serum oxygenated liver.The protein expression of CYP2E1 was reduced in the cells. |
