Intrarenal mRNA expression of the rat MDCK-type chloride channel

We have reported the isolation of a rat cDNA for MDCK-type chloride channel (RKCL) which is expressed in many tissues including the kidney. In the present study, intrarenal expression distribution of RKCL mRNA and the effect of dehydration on its expression were examined. In situ hybridization showed that RKCL mRNA is more abundantly expressed in the renal medulla and papilla than in the cortex. Reverse transcription and polymerase chain reaction using microdissected nephron segments showed that RKCL mRNA is expressed in several nephron segments, notably the ascending thin limb of Henle's loop and inner medullary collecting duct. Under dehydration, renal RKCL mRNA expression level was not significantly changed for 5 days. In conclusion, RKCL mRNA is expressed in most nephron segments, playing a role in the renal tubular chloride ion homeostasis.