Vol. 283, Issue 2, G426-G434, August 2002
Glucocorticoid regulation and glycosylation of mouse
intestinal type IIb Na-Pi cotransporter during
ontogeny
Kayo
Arima,
Eric
R.
Hines,
Pawel R.
Kiela,
Jason B.
Drees,
James F.
Collins, and
Fayez K.
Ghishan
Departments of Pediatrics, Physiology, and Nutritional
Sciences, Steele Memorial Children's Research Center, University of
Arizona Health Sciences Center, Tucson, Arizona 85724
We sought
to characterize expression of an apically expressed intestinal
Na-Pi cotransporter (Na-Pi-IIb) during mouse
ontogeny and to assess the effects of methylprednisolone (MP)
treatment. In control mice, Na-Pi uptake by intestinal
brush-border membrane vesicles was highest at 14 days of age, lower at
21 days, and further reduced at 8 wk and 8-9 mo of age.
Na-Pi-IIb mRNA and immunoreactive protein levels in
14-day-old animals were markedly higher than in older groups. MP
treatment significantly decreased Na-Pi uptake and
Na-Pi-IIb mRNA and protein expression in 14-day-old mice.
Additionally, the size of the protein was smaller in 14-day-old mice.
Deglycosylation of protein from 14-day-old and 8-wk-old animals with
peptide N-glycosidase reduced the molecular weight to the
predicted size. We conclude that intestinal Na-Pi uptake and Na-Pi-IIb expression are highest at 14 days and
decrease with age. Furthermore, MP treatment reduced intestinal
Na-Pi uptake approximately threefold in 14-day-old mice and
this reduction correlates with reduced Na-Pi-IIb mRNA and
protein expression. We also demonstrate that Na-Pi-IIb is
an N-linked glycoprotein and that glycosylation is age dependent.
methylprednisolone; development; Na-Pi-IIb
