Article Figures & Data
Figures
- Fig. 1.
Model scheme describing the hepatobiliary disposition of TVP and metabolites in rat isolated perfused livers. The rate of change in the amount of TVP in perfusate flowing into the first sinusoidal compartment with respect to time,
, was determined by multiplying the inflow concentration (Cin) by the perfusate flow rate (Q). The rate of change in the amount of TVP in the outflow perfusate from the final sinusoidal compartment with respect to time, , was determined by multiplying the outflow concentration (Cout) by Q. Based on the well-stirred model (Pang and Rowland, 1977a,b,c), Cout was assumed to be equal to the concentration in the final sinusoidal compartment, CEC,5. The uptake clearance of TVP from the sinusoidal space to the hepatocellular space was described by CLUP, whereas CLBL described the efflux clearance from the hepatocellular space to the sinusoidal space and CLBile described the clearance of TVP from the hepatocellular space to bile. The biliary excretion rate, , was determined by multiplying the intracellular concentration of TVP (CIC) by the biliary clearance CLBile, as detailed in the differential equations. In the case of polycystic kidney rats, the biliary excretion rates of TVP and DM-4103 + DM-4107 were best described by including transit compartments (XBile,1–5 and X03,07,Bile,1–5, respectively) and transit rate constants (KLag,Bile and KLag,Bile,03,07, respectively) following the excretion of these compounds into bile (denoted by the gray shading). Cytochrome P450–mediated biotransformation of TVP into DM-4103 + DM-4107 and other metabolites occurs in the hepatocellular space, and the formation of these metabolites was described by the clearance parameters CL03,07 and CLMet, respectively. Once DM-4103 and DM-4107 were formed in the hepatocellular space, the hepatobiliary disposition of these metabolites was described with similar clearance parameters as those for TVP, while an uptake clearance parameter for DM-4103 + DM-4107 was not necessary to describe the metabolite profiles. The hepatobiliary disposition of other TVP metabolites could not be assessed directly because only TVP, DM-4103, and DM-4107 concentrations were quantified. Here, XEC and XIC denote the amount of TVP in the extracellular and intracellular space, respectively, and X03,07,EC and X03,07,IC denote the amount of DM-4103 + DM-4107 in the extracellular and intracellular space, respectively. Likewise, VEC, VIC, V03,07,EC, and V03,07,IC denote the volumes of the extracellular and intracellular space for TVP and metabolites, respectively. VEC and V03,07,EC were assumed to be equal; likewise, VIC and V03,07,IC were assumed to be equal. The term CIC,n represents the concentration in the nth liver compartment. - Fig. 2.
Liver recovery of tolvaptan, DM-4103, and DM-4107. Amounts (nmol) of TVP, DM-4103, and DM-4107 recovered at 60 min in isolated perfused livers from WT and PCK rats. Data are presented as mean ± S.D. (n = 6 for WT; n = 5 for PCK).
- Fig. 3.
Outflow perfusate concentration-time profiles. Concentration (nM) vs. time (min) profiles of (A) TVP, (B) DM-4103, and (C) DM-4107 in the outflow perfusate of isolated perfused livers (IPLs) from WT and PCK rats. Statistically significant differences in concentrations between WT and PCK IPLs were assessed at t = 30 and 60 min. Perfusions with tolvaptan (∼7 μM) and subsequently with blank buffer (washout) for 30 min each are represented by the black and gray bars, respectively. Data are presented as mean ± S.D. (n = 6 for WT; n = 5 for PCK). *P < 0.05, PCK vs. WT.
- Fig. 4.
Cumulative bile amount-time profiles. Cumulative amount (nmol) vs. time (min) profiles of (A) TVP, (B) DM-4103, and (C) DM-4107 in the bile of isolated perfused livers (IPLs) from WT and PCK rats. Statistically significant differences in cumulative biliary excretion between WT and PCK IPLs were assessed at 60 min. Perfusions with tolvaptan (∼7 μM) and subsequently with blank buffer (washout) for 30 min each are represented by the black and gray bars, respectively. Data are presented as mean ± S.D. (n = 6 for WT; n = 5 for PCK). *P < 0.05, PCK vs. WT.
- Fig. 5.
Total recovery. Total recovery at 60 min of TVP and two TVP metabolites, DM-4103 and DM-4107, expressed as a percentage of dose, in (A) liver, (B) outflow perfusate, and (C) bile in isolated perfused livers from WT and PCK rats. Significant differences between WT and PCK per sample type were assessed for each of the three chemical species. Data are presented as mean ± S.D. (n = 6 for WT; n = 5 for PCK). *P < 0.05, PCK vs. WT.
- Fig. 6.
Model fits to outflow perfusate appearance and biliary excretion rate-time data. Appearance rate in outflow perfusate (nmol/hr) and biliary excretion rate (nmol/hr) vs. time (min) profiles of [(A and C), respectively] TVP and [(B and D), respectively] DM-4103 + DM-4107 in IPLs from WT and PCK rats. Perfusions with tolvaptan (∼7 μM) and subsequently with blank buffer (washout) for 30 min each are represented by the black and gray bars, respectively. Observed data are presented as mean ± S.D. (n = 6 for WT; n = 5 for PCK). PCKobs and WTobs are the observed outflow perfusate appearance and biliary excretion rates in PCK and WT IPLs, whereas PCKpred and WTpred are the rates predicted by the model scheme depicted in Fig. 1. See Supplemental Fig. 1 for observed vs. predicted outflow perfusate appearance and biliary excretion rate plots.
- Fig. 7.
Simulated hepatocelluar concentrations. Total hepatocellular concentration (nM) vs. time (hr) profiles of (A) TVP and (B) DM-4103 + DM-4107 simulated in the hepatocellular space of isolated perfused livers from WT and PCK rats using the model depicted in Fig. 1. Perfusions with tolvaptan (∼7 μM) and subsequently with blank buffer (washout) for 30 min each are represented by the black and gray bars, respectively.
Tables
- TABLE 1
Estimates of TVP and DM-4103 + DM-4107 clearance values in IPLs from WT and PCK rats based on the model scheme depicted in Fig. 1
Livers were perfused with TVP (∼7 μM) and subsequently with blank buffer (washout) for 30 min each. Statistically significant differences were based on nonoverlapping 95% confidence intervals (CI): *P < 0.05, PCK vs. WT; #P < 0.05, CLBL vs. CLBile within the same rat IPL group; †P < 0.05, compared with CLMet within the same rat IPL group.
Parameter Estimate (CV%); [95% CI] WT PCK CLBL (l/h) 0.20 (20%); [0.12, 0.28]#,† 0.29 (22%); [0.16, 0.43]#,† CLUP (l/h) 21 (14%); [15, 26] 29 (14%); [21, 38] CLBile (l/h) 0.11 × 10−3 (10%); [0.85 × 10−4, 0.13 × 10−3]*,#,† 0.49 × 10−4 (16%); [0.33 × 10−4, 0.65 × 10−4]*,#,† CLMet (l/h) 0.44 × 10−1 (4.2%); [0.40 × 10−1, 0.48 × 10−1] 0.38 × 10−1 (8.9%); [0.31 × 10−1, 0.45 × 10−1] CL03,07 (l/h) 0.18 × 10−2 (20%); [0.10 × 10−2, 0.26 × 10−2]† 0.47 × 10−2 (39%); [0.99 × 10−3, 0.85 × 10−2]† CLBL,03,07 (l/h) 0.50 × 10−2 (24%); [0.26 × 10−2, 0.74 × 10−2] 0.91 × 10−2 (43%); [0.11 × 10−2, 0.17 × 10−1] CLBile,03,07 (l/h) 0.16 × 10−2 (23%); [0.84 × 10−3, 0.24 × 10−2] 0.11 × 10−2 (76%); [−0.62 × 10−3, 0.28 × 10−2] KLag,Bile (h−1) 17 (15%); [12, 22] KLag,Bile,03,07 (h−1) 4.1 (21%); [2.3, 5.8]
Data Supplement
- Supplemental Data -
Supplemental Table 1 - Individual wild-type (WT) and polycystic kidney (PCK) rat outflow perfusate appearance and biliary excretion rates
Supplemental Table 2 - Body and liver weights of wild-type (WT) and polycystic kidney (PCK) rats
Supplemental Figure 1 - Observed (DV) vs. predicted (IPRED) plots of outflow perfusate appearance and biliary excretion rates of tolvaptan (TVP) and DM-4103+DM-4107 in wild-type (A) and polycystic kidney (B) rats.
- Supplemental Data -
In this issue
Disposition of Tolvaptan and Metabolites in PCK Rat Livers
