Pharmacokinetics of Oltipraz in Mutant Nagase Analbuminemic Rats

Pharmacokinetics of drugs in mutant Nagase analbuminemic rats and responses to select diuretics

OBJECTIVES

To report (1) the pharmacokinetics of drugs that are mainly metabolized via hepatic cytochrome P450s (CYPs) or mainly excreted via the urine and bile, (2) the mechanism for the urinary excretion of drugs (such as glomerular filtration or renal active secretion or re-absorption), and (3) the diuretic effect of some loop diuretics in mutant Nagase analbuminaemic rats (NARs), an animal model for human familial analbuminaemia based on the pharmacokinetics of drugs reported in the literatures.

KEY FINDINGS

In NARs, the changes in the time-averaged non-renal clearances (CL(NR)s) of drugs that are mainly metabolized via CYPs were explained in terms of changes in the hepatic intrinsic clearance (mainly because of changes in CYPs), free (unbound) fractions of drugs in the plasma (fp) and hepatic blood-flow rate (QH) depending on the hepatic excretion ratios of drugs.

SUMMARY

The CL(NR) changes of drugs mainly metabolized via hepatic CYPs can be sufficiently explained by the three earlier mentioned factors. The plasma albumin (furosemide) or globulin (azosemide, bumetanide and torasemide) binding affects their diuretic effects.

Role of plasma proteins in pharmacokinetics of micafungin, an antifungal antibiotic, in analbuminemic rats

There were no significant differences in the pharmacokinetics of micafungin and expression of hepatic multidrug resistance-associated protein 2 (ABCC2/Mrp2) between analbuminemic and Sprague-Dawley rats. Micafungin bound strongly to high-density lipoprotein (HDL) and moderately to gamma globulin. These results suggest that HDL and gamma globulin contribute to the pharmacokinetics of micafungin.

Drug-metabolizing enzyme and transporter expression in a mouse model of diabetes and obesity

Obesity and type II diabetes pose a serious human health risk. Obese or diabetic patients usually take prescription drugs that require hepatic and renal metabolism and transport, and these patients sometimes display different pharmacokinetics of these drugs. Therefore, mRNA and protein expression of drug-metabolizing enzymes (DMEs) and transporters was measured in livers and kidneys of adult wild-type and ob/ob mice, which model obesity and diabetes. mRNA expression of numerous DMEs increased by at least 2-fold in livers of male ob/ob mice, including Cyp4a14, Cyp2b10, NAD(P)H:quinone oxidoreductase 1 (Nqo1), and sulfotransferase 2a1/2. In general, expression of uptake transporters was decreased in livers of ob/ob mice, namely organic anion-transporting polypeptides (Oatps) and sodium/taurocholate cotransporting polypeptide (Ntcp). In particular, Oatp1a1 mRNA and protein expression in livers of ob/ob mice was diminished to <5% and <15% of that in wild-types, respectively. Generally, the mRNA and protein expression of efflux transporters multidrug resistance-associated proteins (Mrps) was increased in livers of ob/ob mice, particularly with Mrp4 expression being elevated by at least 6-fold and Mrp2 expression at least 3-fold in livers of ob/ob mice. In kidney, Nqo1, Mrp3, 4, Oatp1a1, and organic anion transporter 2 (Oat2) showed significant alterations with mRNA expression levels in ob/ob mice, being increased for Nqo1 and Mrp4 and decreased for Mrp3, Oatp1a1, and Oat2. In summary, the expression of a number of DMEs and transporters was significantly altered in livers and kidneys of ob/ob mice. Since expression of some DMEs and transporters is regulated similarly between mouse and human, the data from this study suggest that transporter expression in liver and kidney may be changed in patients presenting with obesity and/or type II diabetes.

Pharmacokinetics of intravenous methotrexate in mutant Nagase analbuminemic rats

It has been reported that the plasma (or serum) levels of albumin and globulins were lower and higher, respectively, than the serum levels in control rats. Hence, it could be expected that these changes could affect the renal clearance (Cl(r)) of methotrexate in Nagase analbuminemic rats (NARs) due to changes in plasma protein binding values. Therefore, methotrexate at a dose of 100 mg/kg was administered intravenously to control rats and NARs. The plasma protein binding of methotrexate in NARs was significantly greater (29.4% increase) than the controls, probably due to the considerable binding of the drug (34.2%) to 1.8% beta-plus 0.63% gamma-globulins. The Cl(r) of methotrexate in NARs was significantly slower (36.1% decrease) than the controls, due to the significantly smaller Ae(0-24h) (25.8% decrease). The smaller Ae(0-24h) could be due to the significantly smaller free (unbound to plasma proteins) fractions of methotrexate in plasma (13.8% decrease) in NARs, since methotrexate was mainly excreted in the urine via glomerular filtration. However, the Cl(nr) values were comparable between the control rats and NARs. This could be because methotrexate is not metabolized considerably via hepatic CYP isozymes based on control rats pretreated with SKF 525-A (a nonspecific inhibitor of hepatic CYP isozymes in rats).