| Summary: | The classical physiological enigma of how water crosses biological membranes has recently been solved by the discovery of aquaporins, a large family of homologous membrane proteins which function as highly selective water channels. So far six mammalian aquaporins have been characterised but homologous genes have been found in amphibians, insects, plants and bacteria reflecting the evolutionary conservation and thus likely importance of these molecules. In previous studies in this laboratory, aquaporin-1 mRNA was discovered to be highly expressed in freshly dispersed rat aortic vascular smooth muscle cells. The aims of this project were; [a] to confirm expression of aquaporin-1 in both human and rat vascular smooth muscle cells, [b] to identify any other known or novel aquaporins expresses in these cells and [c] to establish a role for aquaporins in water transport across vascular smooth muscle cell membranes. To attempt this I have used the techniques of northern analysis, western analysis, specific and degenerate PCR, restriction mapping, ABI sequencing, FACS analysis, and immunocytochemistry. Experimentation demonstrated that aquaporin-1 is expressed by human and rat vascular cells both in vivo and in vitro. None of the other known aquaporins are expressed in these cells. No novel aquaporins were identified by nested degenerate PCR [the technique that has been used to discover other novel aquaporins]. Osmotically induced VSMC water conductance is rapid and temperature insensitive implying water transport via membrane channels rather than direct transport across the lipid bilayer. This water transport is inhibitable by mercuric chloride, the only known aquaporin-1 channel inhibitor. These results all suggest that aquaporin-1 may have a role in water homeostasis in vascular smooth muscle cells.
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