| AimsTry to identify whether certain drugs with renal excretion is affected by high serum creatinine level or not, and further investigate the underlying mechanism in order to provide information for dosage adjustment in patients with renal insufficiency.Methods1. Total of 14 male Wistar rats were divided into two groups, the control group and the experimental group. Rats were fasted overnight and anesthetized with ether before experiment. Two polyethylene cannula were inserted into femoral artery and urethra for sample collection, respectively. Rats in control group were intravenously administrated with metformin (25 mg/kg) via the caudal vein, while rats in experimental group were intravenously administrated with metformin (25 mg/kg) and creatinine (720 mg/kg) via the caudal vein. Blood samples were collected from femoral artery using a syringe at 5,10,20,30,45,60,120,240,360,480, and 600 min after drugs administration, the blood sample were then added into heparin-coated polypropylene tubes. Urine sample were collected from the bladder cannula during the interval of 0-2 h,2-4 h,4-6 h,6-8 h,8-10 h,10-24 h after drugs administration. After pharmacokinetic study, kidney tissue was collected in order to evaluate the expression of organic cation transporter 2 (OCT2) and multidrug and toxin extrusion 1 (MATE1) using Western blot technique. The concentration of metformin in plasma and urine were determined by HPLC, data were analyzed by DAS 2.0 software, and the pharmacokinetic parameters, such as AUCO-t, tl/2, CL, ke, etc. were calculated further. In addition, the effect of high creatinine concentration on metformin uptake was also examined by kidney slices of rats. Firstly, we investigated the inhibitory effect of different creatinine concentration on the uptake of metformin (60μM/600μM). The effect of creatinine (10000 μM) on concentration-dependent profile of uptake of metformin (1,10,100,1000,10000 μM) was also studied.2. Total of 14 male Wistar rats were divided into two groups, the control group and the experimental group. Rats were fasted overnight and anesthetized with ether before experiment. The surgical procedures, blood collection and urine collection in rats were as same as that in metformin control group and experimental group, the dosage of ofloxacin was set as 80 mg/kg. After pharmacokinetic study, kidney tissue was collected to evaluate the expression of organic anion transporter 3 (OAT3) and multidrug resistance protein 2 (MRP2) by Western blot technique. The concentration of ofloxacin in plasma and urine were determined by HPLC, data were analyzed by DAS 2.0 software, and the pharmacokinetic parameters, such as AUCo-t, t1/2, CL, ke, etc. were calculated further. In addition, the effect of high creatinine concentration (10000μM) on the uptake of ofloxacin (1,10,100,1000μM) was investigated by kidney slice test.3. Total of 14 male Wistar rats were divided into two groups, the control group and the experimental group. Rats were fasted overnight and anesthetized with ether before experiment. The surgical procedures, blood collection and urine collection in rats were as same as that in metformin control group and experimental group, the dosage of ceftizoxime was set as 300 mg/kg. After pharmacokinetic study, kidney tissue were collected to evaluate the expression of organic anion transporter 3 (OAT3) and multidrug resistance protein 4 (MRP4) by Western blot technique. The concentration of ceftizoxime in plasma and urine were determined by HPLC, data were analyzed by DAS 2.0 software, and the pharmacokinetic parameters, such as AUC0-t, t1/2, CL, ke, etc. were calculated further. In addition, the effect of high creatinine concentration (10000 μM) on the uptake of ceftizoxime (1,10,100,500,1000,5000,10000 μM) was investigated by kidney slice test.Results1. The cumulative urinary excretion of metformin during 0-2 h,0-4 h,0-6 h,0-8 h,0-10 h, 0-24 h urine collection periods in experimental group (3620.438±303.180 μg,3938.058±363.989 μg,4113.592±330.979 μg,4231.314±297.463 μg,4291.704±307.830μg,4392.121±303.609 μg) was significantly decreased comparing with the control group (2920.826±224.088μg, 3194.906±259.651μg,3323.875±231.590μg,3390.747±235.356μg,3431.221±239.132μg, 3535.250±229.255 μg), and plasma concentration of metformin was markedly increased at 2,4,6, 8, and 10 h post creatinine (P<0.05). Compared to that of the control group, the value of AUC and tl/2 in drugs co-administration group were significantly increased (P<0.05), while the value of CL and Ke were markedly decreased (P<0.05). Meanwhile, there was no significant difference in the protein expression of OCT2 and MATE1 between the two groups (P>0.05). In addition, the concentration dependence of metformin uptake by rats kidney slice was significantly inhibited (P<0.05) by high creatinine concentration (10000 μM).2. There was no significant change in the cumulative urinary excretion between experimental group (1840.071±203.586μg,3273.049±98.067μg,3643.884±233.447μg,4089.343±117.249 μg,4415.913±198.199 jig,4819.527±257.641μg) and control group (1474.768±303.258μg, 3020.918±410.508 μg,3706.216±443.377 μg,3993.510±482.005μg,4115.811±445.829 μg, 4655.141±474.286 μg), and there was no significant difference in plasma concentration of ofloxacin between the control group and experimental group (P>0.05). Meanwhile, no significant difference was found in pharmacokinetic parameters (AUC, t1/2, CL, Ke) of ofloxacin between these two groups (P>0.05). After co-administration of creatinine, the protein expression level of OAT3 and MRP2 in experimental group was almost as same as that in control group (P>0.05). In addition, the concentration dependence of ofloxacin uptake in rat kidney slice was not affected (P>0.05) by high creatinine concentration (10000 μM).3. The cumulative urinary excretion of ceftizoxime during 0-2 h,0-4 h,0-6 h,0-8 h,0-10 h, 0-24 h urine collection periods in experimental group (31656.600±629.686μg, 32953.875±1111.083μg,33558.828±1297.117μg,33686.298±1344.036μg,33750.393±1370.018 μg,34026.205±1502.673μg) was significantly decreased comparing with the control group (26046.350±2017.701μg,27180.090±1986.854μg,27425.400±2061.078μg,27470.9±2095.863 μg,27489.970±2110.554μg,27612.390±2106.786μg), and plasma concentration of ceftizoxime was also markedly increased at 2,4,6,8, and 10 h post creatinine (P<0.05). The value of AUC and t1/2 were significantly increased (P><0.05), while the value of CL was markedly decreased (P<0.05). Meanwhile, there was no significant difference in the protein expression of OAT3 and MRP4 between these two groups (P>0.05). In addition, the uptake of ceftizoxime at high concentrations (1000,5000,10000μM) were significantly inhibited in the presence of high creatinine concentration (10000 μM) in rat kidney slice, while the uptake of ceftizoxime at low concentrations (1,10,100,500μM) did not show any alteration in the presence of high creatinine concentration (10000 μM).Conclusion1. High serum creatinine level significantly decreases cumulative urinary excretion of metformin and ceftizoxime, and thus increases the plasma concentration, but has no influence on protein expression of transporters for renal secretion of metformin and ceftizoxime in rats that had normal renal function. Moreover, results from kidney slice study show that high creatinine concentration (10000 μM) could inhibit concentration-dependent uptake of metformin and ceftizoxime in rat. These results indicate that the renal excretion pathway between creatinine and metformin or ceftizoxime may be partial overlapped.2. High serum creatinine level has little effect on cumulative urinary excretion and plasma concentration of ofloxacin, and has no influence on protein expression of transporters for renal secretion of ofloxacin in rats that had normal renal function. Moreover, concentration dependent uptake of ofloxacin by rats kidney slice may not be influenced by high creatinine concentration (10000μM). These results indicat that the renal excretion pathway between creatinine and ofloxacin may not be overlapped. |
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