The effects on aldosterone and vasopressin on the amiloride-sensitive sodium transporter from epithelial tissue will be studied. This transporter has been identified in a particulate fraction of epithelial tissue. It will be further characterized according to sensitivity to changes in pH, ionic strength, temperature, etc. Attempts will be made to reconstitute this transporter into phospholipid vesicles and to purify it with aid of a reconstitution assay.