Vasopressin and hyperosmolality regulate NKCC1 expression in rat OMCD.
Secretory-type Na-K-2Cl cotransporter (NKCC1) is known to play roles in both acid and sodium excretion, and is more abundant in dehydration. To determine the mechanisms by which dehydration stimulates NKCC1 expression, the effects of vasopressin, oxytocin and hyperosmolality on NKCC1 mRNA and protein expressions in the outer medullary collecting duct (OMCD) of rats were investigated using RT-competitive PCR and western blot analysis. Microdissected OMCD was incubated in isotonic or hypertonic solution, or with AVP or oxytocin for 60 min at 37 degrees C. Hyperosmolality induced by NaCl, mannitol or raffinose increased NKCC1 mRNA expression in OMCD by 130-240% in vitro. The stimulation of NKCC1 mRNA expression by NaCl was highest at 690 mosmol kg(-1) H(2)O and gradually decreased at higher osmolalities. The incubation of OMCD with AVP (10(-7) M) for 60 min increased NKCC1 mRNA expression by 100%. The administration of AVP to rats for 4 days using an osmotic mini-pump also increased NKCC1 mRNA and protein expressions in OMCD by 130%. In contrast, oxytocin (10(-7) M) did not stimulate the NKCC1 mRNA expression in OMCD in vitro. Chronic injection of oxytocin increased the NKCC1 mRNA expression by 36%. These data showed that hyperosmolality and vasopressin stimulate NKCC1 mRNA and protein expressions in rat OMCD. It is concluded that NKCC1 expression is regulated directly and indirectly by vasopressin.
Wakamatsu
Shiho
S
Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Honjo, Kumamoto, Japan.
Nonoguchi
Hiroshi
H
Ikebe
Mika
M
Machida
Kenji
K
Izumi
Yuichiro
Y
Memetimin
Hasiyet
H
Nakayama
Yushi
Y
Nakanishi
Takeshi
T
Kohda
Yukimasa
Y
Tomita
Kimio
K
D000818:Animals; D015153:Blotting, Western; D017931:DNA Primers; D003681:Dehydration / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D007685:Kidney Tubules, Collecting / Q000378:metabolism* / Q000473:pathology; D008297:Male; D042282:Microdissection; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012076:Renal Agents / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D028021:Sodium-Potassium-Chloride Symporters / Q000096:biosynthesis* / Q000235:genetics; D064506:Solute Carrier Family 12, Member 2; D014667:Vasopressins / Q000494:pharmacology*; D014883:Water-Electrolyte Imbalance / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology
D017931:DNA Primers; D012333:RNA, Messenger; D012076:Renal Agents; C578879:Slc12a2 protein, rat; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D014667:Vasopressins; D010121:Oxytocin