Cyclic amp activates an atp-conductive pathway in cultured shark rectal gland cells. Cantiello, Horacio F., George R. Jackson, Jr., Adriana G. Prat, J. Lynn Gazley, John N. Forrest, Jr., and Dennis A. Ausiello. Renal Unit, Massachusetts General Hospital East, and Department of Medicine, Harvard Medical School; 2. Department of Medicine, Yale University School of Medicine; 3. Amherst College; 4. The Mount Desert Island Biological Laboratory
APStracts 3:0298C, 1996.
The molecular mechanisms associated with ATP transport and release into the extracellular milieu are largely unknown. To assess the presence of endogenous ATP- conductive pathway(s) in shark rectal gland (SRG) cells, patch-clamp techniques were applied to primary cultures of SRG cells. Whole-cell currents were obtained with either intracellular Tris or Mg salts of ATP (200 mM nominal ATP) and bathing 280 mM NaCl solution. Basal currents showed a sizable ATP permeability for outward movement of MgATP. Cyclic AMP stimulation significantly increased the whole-cell conductance (with either intracellular Tris or MgATP). Symmetrical whole-cell ATP currents were also observed after cAMP activation, thus consistent with ATP as the main charge carrier. The cAMP-inducible ATP currents were insensitive to the Cl- channel blockers DIDS, DPC and 9-AC, but were readily blocked by nifedipine (400 [mu]M) and glibenclamide (400 [mu]M). The nature of the electrodiffusional ATP movement was further assessed by single channel analysis of either Mg- or TrisATP currents in excised, inside-out patches, both spontaneous and after activation with protein kinase A. Single channel ATP currents were inhibited by either nifedipine or glibenclamide. Thus, SRG cells express endogenous, ATP-permeable pathways both prior to and after cAMP -stimulation. Electrodiffusional ATP movement by SRG cells may play a significant role in the transport and delivery of cellular ATP to the extracellular milieu, which may help coordinate the dynamics of the epithelial secretory response in this cell model. 

Received 22 March 1996; accepted in final form 16 August 1996.
APS Manuscript Number C166-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 7 October 1996