TY - JOUR
T1 - Epidermal growth factor inhibits Na-P(i) cotransport in weaned and suckling rats
AU - Arar, Mazen
AU - Zajicek, Hubert K.
AU - Elshihabi, Ihsan
AU - Levi, Moshe
PY - 1999/1
Y1 - 1999/1
N2 - In the present study, we determined the effect of epidermal growth factor (EGF; 10 μg/100 g body wt) on sodium gradient-dependent phosphate transport (Na-P(i) cotransport) regulation in suckling (12-day-old) and weaned (24-day-old) rats. Weaned rats had higher proximal tubular brush border membrane vesicle (BBMV) Na-P(i) cotransport activity (232 ± 16 in weaned vs. 130 ± 9 pmol · 10 s-1 · mg protein-1 in suckling rats, P < 0.05). Chronic treatment with EGF induced inhibition of BBMV Na-P(i) cotransport in both suckling (130 ± 9 vs. 104 ± 7 pmol · 10 s-1 · mg protein-1, P < 0.05) and weaned rats (232 ± 16 vs. 145 ± 9 pmol · 10 s- 1 · mg protein-1, P < 0.005). The inhibitory effect was selective for Na- P(i) cotransport as there was no inhibition of Na-glucose cotransport. Weaned rats had a higher abundance of BBMV NaPi-2 protein than suckling rats (increase of 54%, P < 0.001) and a twofold increase in NaPi-2 mRNA. The EGF- induced inhibition of Na-P(i) transport was paralleled by decreases in NaPi- 2 protein abundance in both weaned (decrease of 26%, P < 0.01) and suckling (decrease of 27%, P < 0.01) animals. In contrast, there were no changes in NaPi-2 mRNA abundance. We conclude that proximal tubule BBMV Na-P(i) cotransport activity, NaPi-2 protein abundance, and NaPi-2 mRNA abundance are higher in weaned than in suckling rats. EGF inhibits Na-P(i) cotransport activity in BBMV isolated from suckling and weaned rats, and this inhibition is mediated via a decrease in NaPi-2 protein abundance, in the absence of a change in NaPi-2 mRNA.
AB - In the present study, we determined the effect of epidermal growth factor (EGF; 10 μg/100 g body wt) on sodium gradient-dependent phosphate transport (Na-P(i) cotransport) regulation in suckling (12-day-old) and weaned (24-day-old) rats. Weaned rats had higher proximal tubular brush border membrane vesicle (BBMV) Na-P(i) cotransport activity (232 ± 16 in weaned vs. 130 ± 9 pmol · 10 s-1 · mg protein-1 in suckling rats, P < 0.05). Chronic treatment with EGF induced inhibition of BBMV Na-P(i) cotransport in both suckling (130 ± 9 vs. 104 ± 7 pmol · 10 s-1 · mg protein-1, P < 0.05) and weaned rats (232 ± 16 vs. 145 ± 9 pmol · 10 s- 1 · mg protein-1, P < 0.005). The inhibitory effect was selective for Na- P(i) cotransport as there was no inhibition of Na-glucose cotransport. Weaned rats had a higher abundance of BBMV NaPi-2 protein than suckling rats (increase of 54%, P < 0.001) and a twofold increase in NaPi-2 mRNA. The EGF- induced inhibition of Na-P(i) transport was paralleled by decreases in NaPi- 2 protein abundance in both weaned (decrease of 26%, P < 0.01) and suckling (decrease of 27%, P < 0.01) animals. In contrast, there were no changes in NaPi-2 mRNA abundance. We conclude that proximal tubule BBMV Na-P(i) cotransport activity, NaPi-2 protein abundance, and NaPi-2 mRNA abundance are higher in weaned than in suckling rats. EGF inhibits Na-P(i) cotransport activity in BBMV isolated from suckling and weaned rats, and this inhibition is mediated via a decrease in NaPi-2 protein abundance, in the absence of a change in NaPi-2 mRNA.
KW - NaPi-2 mRNA
KW - NaPi-2 protein
KW - Phosphate transporter maturation
UR - http://www.scopus.com/inward/record.url?scp=0032917066&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032917066&partnerID=8YFLogxK
U2 - 10.1152/ajprenal.1999.276.1.f72
DO - 10.1152/ajprenal.1999.276.1.f72
M3 - Article
C2 - 9887082
AN - SCOPUS:0032917066
SN - 1931-857X
VL - 276
SP - F72-F78
JO - American Journal of Physiology - Renal Physiology
JF - American Journal of Physiology - Renal Physiology
IS - 1 45-1
ER -