Macrolides are inappropriate as first-choice agents against MRMP in terms of shortening the clinical course and decreasing M. pneumoniae. Control and prevention of MRMP outbreaks in children require early decreases in M. pneumoniae as well as improvement of clinical findings.

Our previous kinetic analyses have shown that the transporter responsible for the renal uptake of pravastatin, an HMG-CoA reductase inhibitor, differs from that involved in its hepatic uptake. Although organic anion transporting polypeptides are now known to be responsible for the hepatic uptake of pravastatin, the renal uptake mechanism has not been clarified yet. In the present study, the involvement of rat organic anion transporter 3 (rOat3; Slc22a8) in the renal uptake of pravastatin was investigated. Immunohistochemical staining indicates the basolateral localization of rOat3 in the kidney. rOat1-and rOat3-expressed LLC-PK1 cells exhibited specific uptake of p-aminohippurate (PAH) and pravastatin, respectively, with the Michaelis-Menten constants (K m values) of 60 M for rOat1-meditad PAH uptake and 13 M for rOat3-mediated pravastatin uptake. Saturable uptake of PAH and pravastatin was observed in kidney slices with K m values of 69 and 11 M, respectively. The difference in the potency of PAH and pravastatin in inhibiting uptake by kidney slices suggests that different transporters are responsible for their renal uptake. This was also supported by the difference in the degree of inhibition by benzylpenicillin, a relatively selective inhibitor of rOat3, for the uptake of PAH and pravastatin by kidney slices. These results suggest that rOat1 and rOat3 are mainly responsible for the renal uptake of PAH and pravastatin, respectively.

Cytochrome P450 (P450) 3A4 is the predominant P450 enzyme expressed in human liver and intestine, and it is involved in the metabolism of approximately 50% of clinically used drugs. Because of the differences in the multiplicity of CYP3A genes and the poor correlation of substrate specificity of CYP3A proteins between species, the extrapolation of CYP3A-mediated metabolism of a drug from animals to man is difficult. This situation is further complicated by the fact that the predictability of the clinically common drug-drug interaction of pregnane X receptor (PXR)-mediated CYP3A4 induction by animal studies is limited as a result of marked species differences in the interaction of many drugs with this receptor. Here we describe a novel multiple humanized mouse line that combines a humanization for PXR, the closely related constitutive androstane receptor, and a replacement of the mouse Cyp3a cluster with a large human genomic region carrying CYP3A4 and CYP3A7. We provide evidence that this model shows a human-like CYP3A4 induction response to different PXR activators, that it allows the ranking of these activators according to their potency to induce CYP3A4 expression in the human liver, and that it provides an experimental approach to quantitatively predict PXR/CYP3A4-mediated drug-drug interactions in humans.

Our previous kinetic analyses have shown that rat organic anion transporter 1 (rOat1; Slc22a6) and rOat3 (Slc22a8) are responsible for the renal uptake of p-aminohippurate and pravastatin, respectively. In this study, their contribution to the renal uptake of organic anions and nucleoside derivatives was examined by investigating the uptake by rOat1-and rOat3-expressing cells and kidney slices. Transfection of rOat1 resulted in an increase of the uptake of temocaprilat (K m ϭ 0.56 M), 2,4-dichlorophenoxyacetate (2,4-D; K m ϭ 10 M), and 3Ј-azido-3Ј-deoxythymidine (AZT; K m ϭ 43 M). rOat3-expressing cells showed significant uptake of temocaprilat (K m ϭ 1.4 M), estrone sulfate (K m ϭ 5.3 M), dehydroepiandrosterone sulfate (DHEAS; K m ϭ 12 M), and benzylpenicillin (PCG; K m ϭ 85 M). All the test compounds were accumulated in kidney slices in a carriermediated manner, although the saturable components of AZT and acyclovir were small. The K m of 2,4-D uptake by kidney slices was comparable with that of rOat1, and the corresponding values of DHEAS and PCG were similar to those of rOat3. The uptake of estrone sulfate and temocapilat by kidney slices consisted of two saturable components, with the K m values of their high-affinity components being similar to those for rOat3 (estrone sulfate), and rOat1 and rOat3 (temocaprilat), respectively. These results suggest that the renal uptake of 2,4-D is mainly accounted for by rOat1 and the uptake of PCG and DHEAS by rOat3, and rOat3 is partly involved in the renal uptake of temocaprilat and estrone sulfate.