Posttranscriptional mechanisms regulate ontogenic changes in rat renal sodium-phosphate transporter.
The present investigation sought to characterize the relationship between ontogeny and Na(+)-P(i) transporter expression in the rat kidney. Results showed that the maximal reaction rate (nmol.mg protein-1.10 s-1) of Na(+)-P(i) transport was highest in 21-day-old rats (2.26 +/- 0.26), was lower in 42- to 45-day-old rats (1.44 +/- 0.19) and 4-mo-old rats (0.78 +/- 0.15), and was lowest in 14-day-old rats (0.50 +/- 0.16) (P = 0.0009, n = 3). The Michaelis constants (mM Pi) were not significantly different in the four age groups. Northern blot analysis revealed that the abundance of Na(+)-P(i) transporter mRNA was similar in all four age groups (n = 5). Western blot analysis demonstrated the highest immunoreactive protein signal in the 21-day-old rat (Na(+)-P(i)/beta-actin = 4.15 +/- 1.16), followed by decreasing protein levels in 42-day-old rats (2.13 +/- 0.22), 4-mo-old rats (0.85 +/- 0.25), and 14-day-old rats (0.75 +/- 0.37) (P = 0.022, n = 5). Immunohistochemical analysis of kidney cortex in the four age groups showed specific staining of only apical membranes in all samples. We conclude that posttranscriptional mechanisms play a role in regulating this transporter during rat ontogeny.
Taufiq
S
S
Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona Health Sciences Center, Tucson 85724, USA.
Collins
J F
JF
Ghishan
F K
FK
D000375:Aging / Q000378:metabolism*; D000818:Animals; D000833:Animals, Suckling / Q000254:growth & development / Q000378:metabolism; D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D007150:Immunohistochemistry; D007668:Kidney / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters
D002352:Carrier Proteins; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters