Vesicular transport as a new paradigm in short-term regulation of transepithelial transport

The vectorial transepithelial transport of water and electrolytes in the re nal epithelium is achieved by the polarized distribution of various transpo rt proteins in the apical and basolateral membrane. The short-term regulati on of transepithelial transport has been traditionally thought to be mediat ed by kinetic alterations of transporter without changing the number of tra nsporters. However, a growing body of recent evidence supports the possibil ity that the stimulus-dependent recycling of transporter-carrying vesicles can alter the abundance of transporters in the plasma membrane in parallel changes in transepithelial transport functions. The abundance of transporte rs in the plasma membrane is determined by net balance between stimulus-dep endent exocytic insertion of transporters into and endocytic retrieval of t hem from the plasma membrane. The vesicular recycling occurs along the trac ts of the actin microfilaments and microtubules with associated motors. Thi s review is to highlight the importance of vesicular transport in the short -term regulatory process of transepithelial transport in the renal epitheli um. In the short-term regulation of many other renal transporters, vesicula r transport is likely to be also involved. Thus, vesicular transport is now emerged as a wide-spread general regulatory mechanism involved in short-te rm regulation of renal functions.