The romk inwardly rectifying atp-sensitive k channel. i. expression in rat distal nephron segments. Lee, Wen-Sen, and Steven C. Hebert. Laboratory of Molecular Physiology and Biophysics, Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School Boston, MA 02115, USA, *Present address: Cardiovascular Biology Laboratory, Harvard School of Public Health, Boston, MA 02115
APStracts 2:0004F, 1995.
The inwardly rectifying, ATP-sensitive potassium channel (ROMK) was localized by in situ hybridization in the rat kidney. Tissue in situ hybridization revealed that transcripts encoding the ROMK channel were expressed predominantly in cortical and outer medullary nephron segments. The localization of ROMK mRNA to specific nephron segments was assessed by hybridization of isolated nephron segments with a ROMK-specific probe [single segment in situ hybridization]. ROMK mRNA was present in cortical and medullary thick ascending limb, distal tubule, cortical and outer medullary collecting duct, but not in proximal tubule. A weak hybridization was observed with inner medullary collecting ducts. To confirm these results, serial cryosections were alternatively stained by hybridization histochemistry for ROMK mRNA or by immunocytochemistry using antibodies specific for S1, S2 or S3 proximal tubular segments. Tubular cells which displayed immunoreactivity with the proximal tubular segment-specific antibodies showed little, if any, ROMK message. In addition, using an in situ hybridization and immunocytochemistry double-labeling technique, ROMK transcripts and vitamin D-dependent calcium binding protein were shown to co -localize to the distal tubule [distal convoluted tubule and connecting tubule]. The overall nephron localization of ROMK mRNA shown in these studies is consistent with the possibility that this novel channel may represent the low conductance ATP-sensitive K+ channel which has been identified in apical membranes of thick limb and collecting duct segments and is believed to participate in potassium secretion. 

Received 7 July 1994; accepted in final form 9 January 1995.
APS Manuscript Number F362-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 February 1995.