Effects of angiotensin II on NaPi-IIa co-transporter expression and activity in rat renal cortex

• Published in: Biochimica et biophysica acta Vol. 1667; no. 2; pp. 114 - 121
• Main Authors: Xu, Liping, Dixit, Mehul P., Chen, Rongji, Dixit, Naznin M., Collins, James F., Ghishan, Fayez K.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.12.2004
• Subjects: Angiotensin II - blood; Angiotensin II - metabolism; Angiotensin II - pharmacology; Animals; Blood Pressure - drug effects; Blotting, Western; Brush-border membrane; Diuresis - drug effects; Glomerular Filtration Rate - drug effects; Infusion Pumps; Kidney; Kidney Cortex - drug effects; Kidney Cortex - metabolism; Kidney Tubules, Proximal - metabolism; Male; Microvilli - drug effects; Microvilli - metabolism; Phosphate transport; Phosphaturia; Rats; Rats, Sprague-Dawley; RNA, Messenger - metabolism; SLC34A1; Sodium-Phosphate Cotransporter Proteins; Sodium-Phosphate Cotransporter Proteins, Type IIa; Symporters - drug effects; Symporters - metabolism; Time Factors; Urine - chemistry; Phosphaturia; Brush-border membrane; SLC34A1; Kidney; Phosphate transport
• ISSN: 0005-2736; 0006-3002; 1879-2642
• DOI: 10.1016/j.bbamem.2004.09.005

The kidney plays a major role in reabsorption of phosphate with the majority occurring in the proximal tubule (PT). The type IIa sodium-phosphate co-transporter (NaPi-IIa) is the main player in PT. The purpose of current study was to determine the effect of angiotensin II (A-II) on membrane expression of NaPi-IIa in the rat renal cortex. A-II (500 ng/kg/min) was chronically infused into the Sprague–Dawley rats by miniosmotic pump for 7 days. The arterial pressure and circulating plasma A-II level along with urine output were markedly increased in A-II rats. There was diuresis but no natriuresis. The phosphate excretion increased sevenfold on day 4 and 5.7-fold on day 7. There was no change in Na-dependent Pi uptake in brush-border membrane (BBM) vesicles between A-II-treated group and control on day 4, however, there was a 43% increase on day 7. Western blot analysis of NaPi-IIa protein abundance showed a parallel pattern: no change after 4 days of treatment and a 48% increase after 7 days of treatment. However, Northern blot analysis of cortical RNA showed no change in NaPi-IIa mRNA abundance on day 7. A-II stimulation of Na/Pi co-transport activity is a result of increases in the expression of BBM NaPi-IIa protein level and that stimulation is most likely mediated by posttranscriptional mechanisms.