Acute regulation of the epithelial sodium channel gene by vasopressin and hyperosmolality.
The amiloride-sensitive epithelial sodium channel (ENaC) plays a key role in sodium reabsorption in the collecting ducts. We examined ENaC mRNA distribution along the nephron and acute effects of vasopressin and hyperosmolality on ENaC mRNA expression. ENaCalpha, beta, and gamma mRNA expressions were observed in cortical, outer medullary and initial inner medullary collecting ducts (CCD, OMCD and ilMCD, respectively). ENaCalpha mRNA expression was also observed in medullary and cortical thick ascending limbs (MAL and CAL, respectively), while ENaCbeta and gamma mRNA expressions were not observed. Furthermore, ENaCalpha mRNA expression in MAL but not in collecting ducts was stimulated by acute exposure to arginine vasopressin (AVP), 8-(4-chlorophenylthio) (CPT)-cAMP and hyperosmolality. However, the physiological significance of these effects is not known, since ENaC protein is reported to be absent in MAL. These data suggest that ENaCalpha mRNA expression in MAL but not in collecting ducts is acutely regulated by AVP and hyperosmolality. The absence of stimulation of ENaCalpha mRNA expression in collecting ducts suggests the physiological significance of ENaCbeta and gamma mRNA for acute regulation by vasopressin. Determining the physiological significance of the acute effect of vasopressin in MAL will require further investigations.
Department of Nephrology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
Kenji
K
Machida
Hiroshi
H
Nonoguchi
Shiho
S
Wakamatsu
Hideki
H
Inoue
Tatjana
T
Yosifovska
Takeaki
T
Inoue
Kimio
K
Tomita
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D053503:Epithelial Sodium Channels; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006982:Hypertonic Solutions / Q000494:pharmacology; D007672:Kidney Cortex / Q000502:physiology; D007679:Kidney Medulla / Q000502:physiology; D007685:Kidney Tubules, Collecting / Q000502:physiology; D008297:Male; D009399:Nephrons / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D012076:Renal Agents / Q000494:pharmacology*; D015222:Sodium Channels / Q000235:genetics* / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D053503:Epithelial Sodium Channels; D006982:Hypertonic Solutions; D012333:RNA, Messenger; D012076:Renal Agents; C507050:Scnn1b protein, rat; D015222:Sodium Channels; D001127:Arginine Vasopressin