Chronic hypercapnia enhances V sub max of Na-H antiporter of renal brush-border membranes

Journal Article · Tue Sep 01 00:00:00 EDT 1987 · American Journal of Physiology; (USA)

OSTI ID:5081309

Talor, Z; Yang, Wuchang; Shuffield, J; Sack, E; Arruda, J A.L. ^[1]

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1. Univ. of Illinois, Chicago (USA)

Chronic hypercapnia is associated with increased proximal HCO{sub 3} reabsorption that is thought to be mediated by a Na-H antiporter. The authors hypothesized that chronic hypercapnia would be associated either with increased V{sub max} or with decreased K{sub m} of the Na-H antiporter. To test this hypothesis they made rabbits hypercapnic for 48 h by exposure to 10% CO{sub 2}. In both control and hypercapnic animals, cortical luminal membranes were enriched over the homogenate 16-fold in alkaline phosphatase and 10-fold in maltase activity. The kinetic activity of the Na-H antiporter was measured by the dissipation of the quenching of acridine orange by addition of different Na concentrations. Chronic hypercapnic rabbits had significantly higher V{sub max} of the Na-H antiporter of luminal membranes than controls. The K{sub m}, however, was not different between control and hypercapnic rabbits. {sup 22}Na uptake in presence of an outwardly directed pH gradient was significantly higher in vesicles from hypercapnic rabbits than controls. Amiloride inhibited the Na-H antiporter (as assessed by acridine orange quenching or {sup 22}Na uptake) to the same degree in membranes from both control and hypercapnic rabbits. The uptake of D-({sup 3}H)glucose by luminal membranes was not different between control and hypercapnic rabbits, indicating a specific enhancement of the Na-H antiporter. Thus chronic hypercapnia, but not acute hypercapnia, induces a selective and specific increase in the V{sub max} of Na-H antiporter, and this may mediate the adaptation to chronic hypercapnia.

• OSTI ID: 5081309
• Journal Information: American Journal of Physiology; (USA), Vol. 253:3; ISSN 0002-9513
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
MEMBRANE PROTEINS
BIOCHEMICAL REACTION KINETICS
SODIUM 22
UPTAKE
UROGENITAL SYSTEM DISEASES
PATHOGENESIS
ACID CARBONATES
ENZYME ACTIVITY
KIDNEYS
PH VALUE
ALKALI METAL ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
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ISOMERIC TRANSITION ISOTOPES
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
SODIUM ISOTOPES
YEARS LIVING RADIOISOTOPES
551001* - Physiological Systems- Tracer Techniques