NonATPMediated Transporters

Several non-ATP-mediated membrane transporter families have been identified, which include organic anion transporting polypeptides (rodent: oatp, human: OATP), organic anion transporters (rodent: oat, human: OAT), organic cation transporters (OCT), and peptide transporters (rodent: pept, human: PEPT). These transporter families play important roles in the disposition and elimination of a variety of endogenous substances, drugs, and their metabolites from the body. The representative members of these families are summarized in Table 2.

Organic Anion Transport Polypeptide (OATP)

Currently, at least nine human OATPs have been identified [30, 31]. OATPs are a group of membrane solute carriers with a wide spectrum of amphipathic substrates [32]. Although some important members of this transporter family are selectively expressed in human livers, most human OATPs are expressed in multiple tissues including the blood-brain barrier (BBB), choroid plexus, heart, intestine, kidney, and placenta [33-38]. Only some of the OATPs so far identified have been characterized in detail at the functional, structural, and genomic levels. Many members of this transporter family represent polyspecific organic anion carriers for transport of a wide range of amphipathic organic solutes. Depending on which side of membrane they are located, OATPs may be responsible for influx or efflux of a wide variety of amphipathic endogenous substances, drugs, and their metabolites.

TABLE 2 Representatives of the Major Human Non-ABC Transporters

TABLE 2 Representatives of the Major Human Non-ABC Transporters

Note: OATP: organic anion-transporting polypeptide; OAT: organic anion transporter; OCT: organic cation transporter.

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