GI262570, a peroxisome proliferator-activated receptor {gamma} agonist, changes electrolytes and water reabsorption from the distal nephron in rats.
Peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists have been shown to have significant therapeutic benefits such as desirable glycemic control in type 2 diabetic patients; however, these agents may cause fluid retention in susceptible individuals. Since PPARgamma is expressed selectively in distal nephron epithelium, we studied the mechanism of PPARgamma agonist-induced fluid retention using male Sprague-Dawley rats treated with either vehicle or GI262570 (farglitazar), a potent PPARgamma agonist. GI262570 (20 mg/kg/day) induced a plasma volume expansion. The plasma volume expansion was accompanied by a small but significant decrease in plasma potassium concentration. Small but significant increases in plasma sodium and chloride concentrations were also observed. These changes in serum electrolytes suggested an activation of the renal mineralocorticoid response system; however, GI262570-treated rats had lower plasma levels of aldosterone compared with vehicle-treated controls. mRNA levels for a group of genes involved in distal nephron sodium and water absorption are changed in the kidney medulla with GI262570 treatment. In addition, due to a possible rebound effect on epithelial sodium channel (ENaC) activity, a low dose of amiloride did not prevent GI262570-induced fluid retention. On the contrary, the rebound effect after amiloride treatment potentiated GI262570-induced plasma volume expansion. This is at least partially due to a synergistic effect of GI262570 and the rebound from amiloride treatment on ENaCalpha expression. In summary, our current data suggest that GI262570 can increase water and sodium reabsorption in distal nephron by stimulating the ENaC and Na,K-ATPase system. This may be an important mechanism for PPARgamma agonist-induced fluid retention.
Department of Molecular Pharmacology, GlaxoSmithKline, Inc., Five Moore Drive, Research Triangle Park, NC 27709, USA. lihong.z.chen@gsk.com
Lihong
L
Chen
Baichun
B
Yang
Judi A
JA
McNulty
Lisa G
LG
Clifton
Jane G
JG
Binz
Angela M
AM
Grimes
Jay C
JC
Strum
W Wallace
WW
Harrington
Zibin
Z
Chen
Thomas W
TW
Balon
Stephen A
SA
Stimpson
Kathleen K
KK
Brown
D000199:Actins / Q000096:biosynthesis; D000450:Aldosterone / Q000097:blood; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001810:Blood Volume / Q000187:drug effects; D004232:Diuretics / Q000494:pharmacology; D004573:Electrolytes / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D053503:Epithelial Sodium Channels; D015870:Gene Expression / Q000187:drug effects; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009399:Nephrons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010080:Oxazoles / Q000494:pharmacology*; D047495:PPAR gamma / Q000819:agonists*; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000096:biosynthesis / Q000235:genetics; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D014867:Water / Q000378:metabolism*
D000199:Actins; D004232:Diuretics; D004573:Electrolytes; D053503:Epithelial Sodium Channels; D010080:Oxazoles; D047495:PPAR gamma; D015222:Sodium Channels; D014867:Water; C422415:farglitazar; D014443:Tyrosine; D000450:Aldosterone; D012313:RNA; D000584:Amiloride; D012964:Sodium