ISSN:
1432-2013
Keywords:
Inorganic phosphate
;
Alkaline phosphatase
;
Kidney
;
Brush borders
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Alkaline phosphatase activity in renal cortex homogenates and in isolated brush border membrane vesicles was compared with the rates of sodium-dependent transport of inorganic phosphate (Pi) by isolated brush border membranes. Brush border membrane vesicles were isolated from renal cortical homogenates of rats adapted during a period of 5–7 weeks to diets with different dietary contents of Pi (low Pi diet=0.15 g%, high Pi diet=2.0 g%). Alkaline phosphatase activity was not increased in the low Pi diet group as compared to the standard Pi diet group but was reduced in the high Pi diet group. Sodium-dependent transport of Pi was increased 2–3-fold in the low Pi diet group as compared to the standard Pi diet group, whereas transport activity was only unsignificantly decreased in the high Pi diet group. Studying kinetik parameters in the two extreme dietary groups it has been found that these differences are due to alteredV max of the transport activity as well as of alkaline phosphatase activity. TheK m for both activities remained unaltered. Alkaline phosphatase activity and transport of Pi in brush border membrane vesicles were also compared in the presence of EDTA or Zn2+ at concentrations which inhibit alkaline phosphatase activity. Transport of Pi was not affected by the inhibitors even when alkaline phosphatase was inhibited by more than 70% (0.5 mmol/l Zn2+) or completely (0.5 mmol/l EDTA). The experiments suggest that no correlation between alkaline phosphatase activity and transport of Pi exists in isolated brush border membrane vesicles.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00584431
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