T4 is light sensitive and known to undergo photodegradation in the presence of colored compounds. the fenamic acid diclofenac inhibited in a competitive manner. Finally, microvessels were isolated from adult rat brain and assessed for T4 uptake. Ten micromolar of fenamate concentrations inhibited T4 microvessel uptake with a similar hierarchical inhibition profile [fenamic acid (43%), diclofenac (78%), and meclofenamic acid (85%)], as observed for Oatp1c1 transfected cells. Oatp1c1 is expressed luminally and abluminally in the blood-brain barrier endothelial cell, and exhibits bidirectional transport capabilities. Together, these data suggest that Oatp1c1 transports fenamates into, and perhaps across, brain barrier cells. Organic anion transporting polypeptides (Oatps) are a large and multifaceted group of membrane-bound solute carriers mediating the transport of amphipathic organic substrates across cellular plasma membranes HLCL-61 (1). HLCL-61 Structurally, all rodent and other animal/human Oatps contain 12- transmembrane spanning domains, a superfamily signature of 13 amino acids and 11 extracellular cysteine residues (2). Substrates of these transporters include steroid conjugates, bile salts, organic dyes, thyroid hormones, and various drugs (3). Rodent and other animal/human Oatp transport mechanisms are sodium independent and likely accomplished through anion exchange (1). Currently, the driving force is unclear, but intracellular glutathione is a potential candidate (4). Many rodent and other animal/human Mouse monoclonal antibody to UCHL1 / PGP9.5. The protein encoded by this gene belongs to the peptidase C12 family. This enzyme is a thiolprotease that hydrolyzes a peptide bond at the C-terminal glycine of ubiquitin. This gene isspecifically expressed in the neurons and in cells of the diffuse neuroendocrine system.Mutations in this gene may be associated with Parkinson disease Oatps are expressed ubiquitously, but more specialized members are expressed exclusively in a limited number of tissues (3). Oatp1c1/OATP1C1 is an Oatp/OATP superfamily member that follows the latter expression and functional pattern. Oatp1c1/OATP1C1 is a high-affinity T4 transporter [reported Michaelis-Menten constant (Km) = 180C720 nm] expressed in the blood-brain barrier (BBB), choroid plexus, human ciliary body epithelium, and Leydig cells of the testis (5,6,7). Other known substrates include rT3, cerivastatin, and estradiol-d-17 -glucuronide (E217G) (8). HLCL-61 Of the Oatps expressed at the BBB, Oatp1c1 has the lowest identified Km for T4, a prohormone that plays a crucial role in the timing of multiple neurological development processes (9). An extensive network of microvessels infiltrates the brain and is comprised of brain capillary endothelial cells that together form the BBB. Unlike other tissues in which solutes in the blood enter the parenchyma through diffusion between endothelial cells, brain capillary endothelial cells possess HLCL-61 tight junctions that prevent paracellular diffusion. As a result, solutes must cross the luminal and abluminal membranes of the brain capillary endothelial cell to enter the brain parenchyma. Such transport is accomplished by a number of solute carriers, including the Oatps (10,11). Oatp1c1 is the fourth most abundant transporter expressed in rat brain endothelial cells (12,13). Oatp1c1 protein has been localized to both the luminal and abluminal side of brain endothelial cells, and implicated in the transport of T4 HLCL-61 across the BBB. T4 is an important regulator of brain development (8,12,14). In addition, Oatp1c1 is also localized to cells comprising the blood-cerebrospinal fluid barrier. Unlike other regions of the brain, choroid plexus vasculature is fenestrated, and the barrier is formed through tight junctions between epithelial cells (15). Currently, Oatp1c1 is thought to be localized to the basolateral membrane of choroid plexus epithelial cells (1). Identifying Oatp1c1 and other brain transporter substrates is important in understanding drug-drug interactions or drug-hormone interactions and for the rational design of new drugs. A comprehensive knowledge of substrate specificity will assist in the design of drugs to facilitate or inhibit uptake via brain transporters. Compared with other Oatps, Oatp1c1 has relatively narrow substrate specificity. Our current study sought to identify novel Oatp1c1 substrates. In addition, we sought to elucidate possible functional consequences of Oatp1c1-mediated transport of these substances. Candidates were identified from known competitive inhibitors of thyroid hormone transport (16). Because T4 is transported by Oatp1c1, we hypothesized that some of these known thyroid hormone transport inhibitors may be specific Oatp1c1 inhibitors and/or substrates. Amiodarone, bilirubin, phenytoin, iopanoic acid, indocyanine green (ICG), and members of the fenamic acid family of nonsteroidal antiinflammatory drugs (NSAIDs) were among the compounds tested for Oatp1c1-specific T4 transport inhibition using a model cell line overexpressing Oatp1c1. We found that the fenamic acid diclofenac competitively inhibited T4 uptake by Oatp1c1. In addition, the fenamates inhibited T4 uptake in isolated rat brain microvessels using an transport assay. Molecular.