Post-transcriptional mechanisms regulate ontogenic changes in the
rat renal sodium-phosphate transporter.
Taufiq, Salik, James F. Collins, and Fayez K. Ghishan.
Departments of Pediatrics and Physiology, Steele Memorial
Children's Research Center, University of Arizona Health Sciences
Center, Tucson, AZ 85724
APStracts 3:0227R, 1996.
The present investigation sought to characterize the relationship
between ontogeny and Na+/Pi transporter expression in the rat kidney.
Results showed that the Vmax (nmol/mg protein/10 sec.) of Na+/Pi
transport was highest in 21 day rats (2.26 +/- 0.26), was lower in
42-45 day rats (1.44 +/- 0.19) and 4 month rats (0.78 +/- 0.15),and
was lowest in 14 day rats (0.50 +/- 0.16) [p= 0.0009, n=3]. The Km
values (mM Pi) were not significantly different in the 4 age groups.
Northern blot analysis revealed that the abundance of Na+/Pi
transporter mRNA was similar in all four age groups (n=5). Western
blot analysis demonstrated the highest immunoreactive protein signal
in the 21 day rat (Na+-Pi/[beta]-actin = 4.15 +/- 1.16), followed by
decreasing protein levels in 42 day rats (2.13 +/- 0.22), 4 month
rats (0.85 +/- 0.25) and 14 day rats (0.75 +/- 0.37) [p=0.022, n=5].
Immunohistochemical analysis of kidney cortex in the 4 age groups
showed specific staining of only apical membranes in all samples. We
conclude that post-transcriptional mechanisms play a role in
regulating this transporter during rat ontogeny.
Received 1 March 1996; accepted in final form 4 June 1996.
APS Manuscript Number R126-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96