Kinetics, stoichiometry, and anion selectivity of cAMP-stimulated Cl-HCO/sub 3/ exchange in rabbit cortical collecting tubule (CCT)

Conference · Fri Feb 28 23:00:00 EST 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5393331

Schuster, V L

Cyclic AMP stimulates net HCO/sub 3/ secretion in rabbit CCT (Schuster, JCI 75:2056). Because cAMP induces Cl-independent (electrogenic) HCO/sub 3/ secretion in several epithelia, I studied the anion dependence of the CCT cAMP effect. Tubules were perfused in vitro with lumen amiloride; bath cAMP was continuously present to stimulate HCO/sub 3/ secretion. First, the dependence of HCO/sub 3/ secretion on lumen (Cl) was determined. With bath (Cl)=O mM, perfusate (Cl) was varied (2-150 mM, gluconate substitution). Mean lumen (Cl) was determined either by a silver electrode in the collected fluid (2-12 mM perfusate) or by /sup 36/Cl (12-150 mM). Total bath-to-lumen HCO/sub 3/ flux, J/sup Ib//sub HCO3/, was measured (bath HCO/sub 3/=25 mM, perfusate HCO/sub 3/=O), Passive J/sub HCO3/ was estimated from the GHK equation using a previously-determined HCO/sub 3/ permeability = 1.9 x 10/sup -6/ cm/s. Mediated J/sub HCO3/ vs. mean lumen (Cl) showed saturation kinetics, apparent K/sub m/ = 5.8 mM and V/sub max/ = 8.7 pmol/mm/min. Second, the stoichiometry was estimated. When bath HCO/sub 3/ was replaced by HEPES at various perfusate (Cl) (12-150 mM), ..delta..J/sub HCO3/ varied linearly with ..delta..J/sup Ib/sub Cl/ (slope = .85 +- .27). Third, in anion selectivity studies Br supported HCO/sub 3/ secretion (89% rate with Cl) but I/sup -/ and SO/sub 4//sup =/ did not. In rabbit CCT, as opposed to several other HCO/sub 3/-secreting epithelia, cAMP stimulates 1:1 Cl-HCO/sub 3/ exchange.

• Research Organization: Univ. of Iowa, Iowa City
• OSTI ID: 5393331
• Report Number(s): CONF-8604222-
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:3; ISSN FEPRA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACID CARBONATES
AMP
ANIMAL TISSUES
ANIMALS
ANIONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CHARGED PARTICLES
CHLORINE 36
CHLORINE COMPOUNDS
CHLORINE ISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ELECTROPHYSIOLOGY
EPITHELIUM
HALOGEN COMPOUNDS
ION EXCHANGE
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KIDNEYS
KINETICS
LIGHT NUCLEI
MAMMALS
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANS
PERFUSED TISSUES
PHYSIOLOGY
RABBITS
RADIOISOTOPES
REACTION KINETICS
SECRETION
STOICHIOMETRY
TISSUES
TRACER TECHNIQUES
TUBULES
VERTEBRATES
YEARS LIVING RADIOISOTOPES