TY - JOUR
T1 - Cellular mechanisms of acute and chronic adaptation of rat renal P(i) transporter to alterations in dietary P(i)
AU - Levi, M.
AU - Lotscher, M.
AU - Sorribas, V.
AU - Custer, M.
AU - Arar, M.
AU - Kaissling, B.
AU - Murer, H.
AU - Biber, J.
PY - 1994
Y1 - 1994
N2 - Recently, the cDNA for a Na-P(i) cotransport system of rat kidney cortex (NaPi-2) has been identified by expression cloning. Using polyclonal antibodies raised against this renal Na-P(i) cotransport system, and using the polymerase chain reaction after reverse transcription of mRNA in microdissected nephron segments, we recently demonstrated that NaPi-2- related mRNA and protein is expressed in the brush-border membranes (BBM) of the proximal tubules of rat kidney. The purpose of the present study was to study the cellular mechanisms involved in adaptation of rat renal Na-P(i) cotransporter to acute and chronic alterations in dietary P(i). Compared with rats fed chronically (7 days) a high-P(i) diet (1.2%), in rats fed chronically a low-P(i) (0.1%) diet the 3.4-fold increase in BBM Na-P(i) cotransport rate (chronic upregulation) was associated with a 2.2-fold increase in renal cortical NaPi-2 mRNA and a 4.9-fold increase in BBM NaPi-2 protein abundances. In contrast, compared with rats fed chronically (7 day) a high-P(i) diet, in rats fed acutely (2 h) a low-P(i) diet the 1.5-fold increase in Na-P(i) cotransport rate (acute upregulation) was associated with a 1.8-fold increase in NaPi-2 protein but no change in NaPi-2 mRNA abundance. Similarly, compared with rats fed chronically a low-P(i) diet, in rats fed acutely (2 h) a high-P(i) diet the 1.9-fold decrease in Na-P(i) cotransport rate (acute downregulation) was associated with a 3.8-fold decrease in NaPi- 2 protein but no change in NaPi-2 mRNA abundance. The results suggest that under chronic conditions protein synthesis is involved in the adaptive response to alterations in dietary P(i) content. On the other hand, under acute conditions the number of Na-P(i) cotransporters in the proximal tubular BBM can be rapidly changed by mechanisms independent of protein synthesis.
AB - Recently, the cDNA for a Na-P(i) cotransport system of rat kidney cortex (NaPi-2) has been identified by expression cloning. Using polyclonal antibodies raised against this renal Na-P(i) cotransport system, and using the polymerase chain reaction after reverse transcription of mRNA in microdissected nephron segments, we recently demonstrated that NaPi-2- related mRNA and protein is expressed in the brush-border membranes (BBM) of the proximal tubules of rat kidney. The purpose of the present study was to study the cellular mechanisms involved in adaptation of rat renal Na-P(i) cotransporter to acute and chronic alterations in dietary P(i). Compared with rats fed chronically (7 days) a high-P(i) diet (1.2%), in rats fed chronically a low-P(i) (0.1%) diet the 3.4-fold increase in BBM Na-P(i) cotransport rate (chronic upregulation) was associated with a 2.2-fold increase in renal cortical NaPi-2 mRNA and a 4.9-fold increase in BBM NaPi-2 protein abundances. In contrast, compared with rats fed chronically (7 day) a high-P(i) diet, in rats fed acutely (2 h) a low-P(i) diet the 1.5-fold increase in Na-P(i) cotransport rate (acute upregulation) was associated with a 1.8-fold increase in NaPi-2 protein but no change in NaPi-2 mRNA abundance. Similarly, compared with rats fed chronically a low-P(i) diet, in rats fed acutely (2 h) a high-P(i) diet the 1.9-fold decrease in Na-P(i) cotransport rate (acute downregulation) was associated with a 3.8-fold decrease in NaPi- 2 protein but no change in NaPi-2 mRNA abundance. The results suggest that under chronic conditions protein synthesis is involved in the adaptive response to alterations in dietary P(i) content. On the other hand, under acute conditions the number of Na-P(i) cotransporters in the proximal tubular BBM can be rapidly changed by mechanisms independent of protein synthesis.
KW - brush-border membrane
KW - inorganic phosphate
KW - sodium gradient-dependent phosphate transporter
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U2 - 10.1152/ajprenal.1994.267.5.f900
DO - 10.1152/ajprenal.1994.267.5.f900
M3 - Article
C2 - 7977794
AN - SCOPUS:0027987883
SN - 0363-6127
VL - 267
SP - F900-F908
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
IS - 5 36-5
ER -