CRAWFORD, Alisa*; DECKER, Sarah; KELLEY, Catherine; BELTZ, Eleanor; TELLES, Conner; RATNER, Martha; EPSTEIN, Max; FORREST, John N. Jr.; Medgar Evers College; Yale Univ. School of Medicine; Skidmore College; Colby College; Yale Univ. School of Medicine; Mount Desert Island Biological Laboratory; Mount Desert Island Biological Laboratory; Mount Desert Island Biological Laboratory: Identifying the specific basolateral potassium channel that is involved in Cl- secretion of the spiny dogfish (Squalus acanthias)

The shark rectal gland is homologous to the thick ascending limb of the Loop of Henle in mammalian kidney. It serves as a model to study how chloride is secreted through Cystic Fibrosis Transmembrane Conductance Regulator channels. The dogfish shark has been in existence for over four hundred million years. The shark relies on a specialized organ, the shark rectal gland (SRG), to assist the kidney in maintaining salt balance. The SRG is made up of tubular epithelial cells. Therefore, when analyzing the effects of various compounds, the responses observed are those of the epithelial cells in the rectal gland. We sought to determine the identity of the specific basolateral potassium channel involved in Cl- secretion. Previously our laboratory showed that bupivacaine and quinine, which are specific inhibitors of 2P, 4TM K+ channels, inhibited chloride secretion in the in vitro perfused rectal gland of the Squalus acanthias. BaCl2 (5 mM) completely blocked Cl- secretion in perfused glands. Rectal glands from male and female S. acanthias were cannulated and perfused. Volume of duct solution secreted, as well as the chloride concentration was measured. We examined the effects of Phentolamine (200 µM) and Charybdotoxin (50 nM), which are both inhibitors of the Ca+ sensitive Cl- channels of the 4TM, 2P K+ channel. We observed that they have no Ba+ affect to inhibit secretion. In further studies our lab has cloned and expressed a TASK-1 channel from the SRG. This channel is undergoing further characterization using electrophysiological methods.