Long-term contact with antivirals is associated with serious cellular toxicity to the kidney and other tissues. staining approach combined with fluorescent uptake in WEK cultures allowed LAP18 the visualization of OAT-mediated uptake into developing proximal tubule-like structures as well as quantification of substrate interactions of individual OAT isoforms. In general antiviral specificity of SLC22a6 (Oat1) (in Oat3-/- WEK culture) and SLC22a8 (Oat3) (in Oat1-/- WEK culture) was consistent with the oocyte data. The combined observations suggest SLC22a8 (Oat3) is the major transporter interacting with ddC and ddI. Finally quantitative structure-activity relationship VP-16 analysis of the nine antivirals’ VP-16 physicochemical descriptors with their OAT affinity indicates that antiviral preferences of mOat1 are explained VP-16 by high polar surface areas (phosphate groups) whereas mOat3 prefers hydrogen bond acceptors (amines ketones) and low rotatable bond numbers. In contrast hydrogen bond donors (amides alcohols) diminish binding to mOat6. This suggests that despite sharing close overall sequence homology Oat1 Oat3 and Oat6 have signficantly different binding pockets. Taken together the VP-16 data provide a basis for understanding potential drug interactions in combination antiviral therapy as well as suggesting structural mdifications for drug design especially in the context of targeting toward or away from specific tissues. The organic anion transporters (OATs)2 mediate the uptake of structurally diverse substrates: endogenous substances (steroids odorants cyclic nucleotides neurotransmitters) medications (nonsteroidal anti-inflammatory medications diuretics and antibiotics) environmental poisons (ochratoxin A and mercuric chlorides) and various other organic wastes (1 2 It has been hypothesized that OATs and other SLC22 family members participate in a remote sensing mechanism for small molecules between tissues and also between organisms (1 23 The prototype now called Oat1 was initially identified as NKT (3-5). Since then at least six OATs have been identified all of which are members of the larger SLC22 family of transporters. Most closely related to SLC22a6 (Oat1) are SLC22a8 (Oat3) originally identified as Roct (6) and the recently identified SLC22a20 (Oat6) expressed in olfactory mucosa (1 7 Importantly the OATs have been postulated to constitute the initial step in the uptake of antiviral nucleoside and nucleobase analog antiretroviral uptake (8 9 To combat chronic disease VP-16 because of HIV herpes smallpox and other viruses antiviral drugs are often administered with HIV also requiring prolonged combination therapies as either triple or quadruple drug “cocktails” (10). Unfortunately long-term exposure to antivirals is often associated with nephrotoxicity lactic acidosis hepatic failure and skeletal myopathy (11 12 problems that can be further exacerbated by additional as yet undefined drug interactions. Despite their plausible VP-16 role via OAT transport in cytotoxicity data in the comparative affinity of antiviral medications for OATs (or IC50) is bound mainly to Oat1 (13 14 with some data indicating the participation of Oat3 (15-17). Nevertheless the comparative contribution of every OAT towards the uptake of antivirals in epithelial and various other tissues is unidentified. The analysis is confounded by the current presence of multiple simultaneously expressed transporters further; varying levels of substrate specificity on the (specific) transporter level; and a complicated pattern of tissues expression and mobile localization. These problems have yet to become addressed within a program or within a set of tests; however trusted heterologous systems for addressing OAT affinity usually do not take these presssing issues into consideration. In the initial explanation of NKT/Oat1 it had been shown the fact that gene is portrayed during kidney advancement (4). Whole organ culture could conceivably provide a system for studying substrate interactions in a total environment providing native cellular machinery recapitulating the whole tissue response and the whole organ system to determine the affinity values for any subset of nucleotide reverse transcriptase inhibitors (NRTI) and acyclic nucleotide/nucleoside antivirals interacting with mOat1 mOat3 and mOat6: adefovir cidofovir tenofovir acyclovir ddC ddI 3 d4T and AZT (21). We demonstrate that mouse WEKs can be utilized for quantitative analyses and using a novel live organ lectin staining process localize unique proximal tubule-like uptake patterns in WEK. By using mOat1 and.