Lawrence G Palmer   Professor of Physiology and Biophysics

CELLULAR AND MOLECULAR BASIS OF EPITHELIAL ION TRANSPORT

The kidney precisely controls the levels of electrolytes in the plasma. This function is vital, as the body requires a constant internal milieu to function properly. Our laboratory is interested in the cellular and molecular events involved in the transport of Na and K between blood and urine, and in the hormonal mechanisms underlying the regulation of these transport processes. These studies have led us to two key transport proteins: Na - and K -selective ion channels in the apical membrane of the mammalian cortical collecting tubule. This is the segment of the nephron that is most sensitive to hormones and that oversees the fine control of plasma Na and K . The channels control the reabsorption of Na from and the secretion of K into the urine. We have identified these transporters using the patch-clamp technique, which allows the study of single channel molecules in living cell membranes. With this approach we can study the properties of individual ion channels-channel density, conductance, and open probability-in the living cell membrane. We are investigating the influence of previous dietary and hormonal history on channel densities. In addition, we are investigating the acute regulation of the channels by membrane voltage, intracellular pH and Ca2 , and phosphorylation. At the molecular level, we have isolated a cDNA clone for a renal K channel, and clones for the epithelial Na channel have been identified by others. We are now using these molecular tools to study the long-term control of the channels at the genetic level by measuring changes in mRNA and protein. We are also using site-directed mutagenesis to investigate the parts of the proteins which determine channel conductivity, selectivity and gating. Our long-term goals are to understand at the molecular level how ions move across epithelial cell membranes, and how this movement is regulated to suit the needs of the organism. e-mail: lgpalm@med.cornell.edu Further Information: http://physiology.med.cornell.edu/faculty/palmer/index.html

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  • lgpalm@med.cornell.edu