Characterization and expression of a novel Na+-inorganic phosphate transporter at the liver plasma membrane of the rat

Fayez K Ghishan, Rwanda Rebeiz, Tatsuya Honda, Nozomu Nakagawa

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Background: Phosphate transport across the plasma membrane of the intestine and kidney occur by an Na+-dependent process. The mechanism by which phosphate enters the hepatocytes across the basolateral membrane is not known. Therefore, our study was designed to investigate whether the plasma membranes of the liver possess a specialized transport system for translocation of phosphate into the hepatocyte. Methods: Liver plasma membrane vesicles and expression of liver poly(A)+ RNA into Xenopus laevis oocytes was used. Results: Phosphate was driven into the intravesicular space as depicted by the equation y = 493.96x + 0.001, r2 = 0.96. Inwardly directed Na+ and pH gradients stimulated phosphate uptake, with a Vmax of 0.58 ± 0.03 and 0.22 ± 0.03 nmol/mg protein/10 s, at pH 6.1 and 7.4, respectively (P < 0.05). Km values were 0.39 ± 0.07 and 0.25 ± 0.1 mmol/L, respectively. To confirm the presence of a phosphate carrier, the liver Na+ phosphate transporter was expressed in X. laevis oocytes. The size-selected messenger RNA encoding for the phosphate transporter was 1.6 kilobases (kb) with kinetic parameters of Vmax 6.75 ± 0.9 pmol/mg protein/5 min and Km of 0.29 ± 0.1 mmol/L, compared with a Vmax of 0.41 ± 0.03 pmol/mg protein/5 min and a Km of 0.085 ± 0.022 mmol/L for water injection. Colonic poly(A)+ RNA did not stimulate phosphate uptake in the oocytes. Conclusion: The combined studies of plasma membrane vesicles and the expression system into X. laevis oocytes confirm the presence of an Na+-phosphate transporter at the liver plasma membranes.

Original languageEnglish (US)
Pages (from-to)519-526
Number of pages8
JournalGastroenterology
Volume105
Issue number2
StatePublished - 1993
Externally publishedYes

Fingerprint

Phosphate Transport Proteins
Phosphates
Cell Membrane
Oocytes
Liver
Xenopus laevis
Messenger RNA
Hepatocytes
Proteins
Proton-Motive Force
Intestines
Kidney
Injections
Membranes
Water

ASJC Scopus subject areas

  • Gastroenterology

Cite this

Characterization and expression of a novel Na+-inorganic phosphate transporter at the liver plasma membrane of the rat. / Ghishan, Fayez K; Rebeiz, Rwanda; Honda, Tatsuya; Nakagawa, Nozomu.

In: Gastroenterology, Vol. 105, No. 2, 1993, p. 519-526.

Research output: Contribution to journalArticle

Ghishan, Fayez K ; Rebeiz, Rwanda ; Honda, Tatsuya ; Nakagawa, Nozomu. / Characterization and expression of a novel Na+-inorganic phosphate transporter at the liver plasma membrane of the rat. In: Gastroenterology. 1993 ; Vol. 105, No. 2. pp. 519-526.
@article{22a79587ae0d45f1b838a3e778f3b0f8,
title = "Characterization and expression of a novel Na+-inorganic phosphate transporter at the liver plasma membrane of the rat",
abstract = "Background: Phosphate transport across the plasma membrane of the intestine and kidney occur by an Na+-dependent process. The mechanism by which phosphate enters the hepatocytes across the basolateral membrane is not known. Therefore, our study was designed to investigate whether the plasma membranes of the liver possess a specialized transport system for translocation of phosphate into the hepatocyte. Methods: Liver plasma membrane vesicles and expression of liver poly(A)+ RNA into Xenopus laevis oocytes was used. Results: Phosphate was driven into the intravesicular space as depicted by the equation y = 493.96x + 0.001, r2 = 0.96. Inwardly directed Na+ and pH gradients stimulated phosphate uptake, with a Vmax of 0.58 ± 0.03 and 0.22 ± 0.03 nmol/mg protein/10 s, at pH 6.1 and 7.4, respectively (P < 0.05). Km values were 0.39 ± 0.07 and 0.25 ± 0.1 mmol/L, respectively. To confirm the presence of a phosphate carrier, the liver Na+ phosphate transporter was expressed in X. laevis oocytes. The size-selected messenger RNA encoding for the phosphate transporter was 1.6 kilobases (kb) with kinetic parameters of Vmax 6.75 ± 0.9 pmol/mg protein/5 min and Km of 0.29 ± 0.1 mmol/L, compared with a Vmax of 0.41 ± 0.03 pmol/mg protein/5 min and a Km of 0.085 ± 0.022 mmol/L for water injection. Colonic poly(A)+ RNA did not stimulate phosphate uptake in the oocytes. Conclusion: The combined studies of plasma membrane vesicles and the expression system into X. laevis oocytes confirm the presence of an Na+-phosphate transporter at the liver plasma membranes.",
author = "Ghishan, {Fayez K} and Rwanda Rebeiz and Tatsuya Honda and Nozomu Nakagawa",
year = "1993",
language = "English (US)",
volume = "105",
pages = "519--526",
journal = "Gastroenterology",
issn = "0016-5085",
publisher = "W.B. Saunders Ltd",
number = "2",

}

TY - JOUR

T1 - Characterization and expression of a novel Na+-inorganic phosphate transporter at the liver plasma membrane of the rat

AU - Ghishan, Fayez K

AU - Rebeiz, Rwanda

AU - Honda, Tatsuya

AU - Nakagawa, Nozomu

PY - 1993

Y1 - 1993

N2 - Background: Phosphate transport across the plasma membrane of the intestine and kidney occur by an Na+-dependent process. The mechanism by which phosphate enters the hepatocytes across the basolateral membrane is not known. Therefore, our study was designed to investigate whether the plasma membranes of the liver possess a specialized transport system for translocation of phosphate into the hepatocyte. Methods: Liver plasma membrane vesicles and expression of liver poly(A)+ RNA into Xenopus laevis oocytes was used. Results: Phosphate was driven into the intravesicular space as depicted by the equation y = 493.96x + 0.001, r2 = 0.96. Inwardly directed Na+ and pH gradients stimulated phosphate uptake, with a Vmax of 0.58 ± 0.03 and 0.22 ± 0.03 nmol/mg protein/10 s, at pH 6.1 and 7.4, respectively (P < 0.05). Km values were 0.39 ± 0.07 and 0.25 ± 0.1 mmol/L, respectively. To confirm the presence of a phosphate carrier, the liver Na+ phosphate transporter was expressed in X. laevis oocytes. The size-selected messenger RNA encoding for the phosphate transporter was 1.6 kilobases (kb) with kinetic parameters of Vmax 6.75 ± 0.9 pmol/mg protein/5 min and Km of 0.29 ± 0.1 mmol/L, compared with a Vmax of 0.41 ± 0.03 pmol/mg protein/5 min and a Km of 0.085 ± 0.022 mmol/L for water injection. Colonic poly(A)+ RNA did not stimulate phosphate uptake in the oocytes. Conclusion: The combined studies of plasma membrane vesicles and the expression system into X. laevis oocytes confirm the presence of an Na+-phosphate transporter at the liver plasma membranes.

AB - Background: Phosphate transport across the plasma membrane of the intestine and kidney occur by an Na+-dependent process. The mechanism by which phosphate enters the hepatocytes across the basolateral membrane is not known. Therefore, our study was designed to investigate whether the plasma membranes of the liver possess a specialized transport system for translocation of phosphate into the hepatocyte. Methods: Liver plasma membrane vesicles and expression of liver poly(A)+ RNA into Xenopus laevis oocytes was used. Results: Phosphate was driven into the intravesicular space as depicted by the equation y = 493.96x + 0.001, r2 = 0.96. Inwardly directed Na+ and pH gradients stimulated phosphate uptake, with a Vmax of 0.58 ± 0.03 and 0.22 ± 0.03 nmol/mg protein/10 s, at pH 6.1 and 7.4, respectively (P < 0.05). Km values were 0.39 ± 0.07 and 0.25 ± 0.1 mmol/L, respectively. To confirm the presence of a phosphate carrier, the liver Na+ phosphate transporter was expressed in X. laevis oocytes. The size-selected messenger RNA encoding for the phosphate transporter was 1.6 kilobases (kb) with kinetic parameters of Vmax 6.75 ± 0.9 pmol/mg protein/5 min and Km of 0.29 ± 0.1 mmol/L, compared with a Vmax of 0.41 ± 0.03 pmol/mg protein/5 min and a Km of 0.085 ± 0.022 mmol/L for water injection. Colonic poly(A)+ RNA did not stimulate phosphate uptake in the oocytes. Conclusion: The combined studies of plasma membrane vesicles and the expression system into X. laevis oocytes confirm the presence of an Na+-phosphate transporter at the liver plasma membranes.

UR - http://www.scopus.com/inward/record.url?scp=0027181048&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0027181048&partnerID=8YFLogxK

M3 - Article

C2 - 8335206

AN - SCOPUS:0027181048

VL - 105

SP - 519

EP - 526

JO - Gastroenterology

JF - Gastroenterology

SN - 0016-5085

IS - 2

ER -