Ionic regulation of Na absorption in proximal colon: cation inhibition of electroneutral Na absorption

Journal Article · Thu Jan 01 04:00:00 EST 1987 · Am. J. Physiol.; (United States)

OSTI ID:6409185

Sellin, J H; De Soignie, R

Active Na absorption (J/sub net//sup NA/) in rabbit proximal colon in vitro is paradoxically stimulated as (Na) in the bathing media is lowered with constant osmolarity. J/sub m..-->..s//sup Na/ increases almost linearly from 0 to 50 mM (Na)/sub 0/ but then plateaus and actually decreases from 50 to 140 mM (Na)/sub 0/, consistent with inhibition of an active transport process. Both lithium and Na are equally effective inhibitors of J/sub net//sup Na/, whereas choline and mannitol do not block the high rate of J/sub net//sup Na/ observed in decreased (Na)/sub 0/. Either gluconate or proprionate replacement of Cl inhibits J/sub net//sup Na/. J/sub net//sup Na/ at lowered (Na)/sub 0/ is electrically silent and is accompanied by increased Cl absorption; it is inhibited by 10/sup -3/ M amiloride and 10/sup -3/ theophylline but not by 10/sup -4/ M bumetanide. Epinephrine is equally effective at stimulating Na absorption at 50 and 140 mM (Na). Na gradient experiments are consistent with a predominantly serosal effect of the decreased (Na)/sub 0/. These results suggest that 1) Na absorption in rabbit proximal colon in vitro is stimulated by decreased (Na); 2) the effect is cation specific, both Na and Li blocking the stimulatory effect; 3) the transport is mediated by Na-H exchange and is Cl dependent but 4) is under different regulatory mechanisms than the epinephrine-sensitive Na-Cl cotransport previously described in proximal colon. Under the appropriate conditions, proximal colon absorbs Na extremely efficiently. Na-H exchange in this epithelium is cation inhibitable, either directly or by a secondary regulatory process.

• Research Organization: Univ. of Texas Medical School, Houston
• OSTI ID: 6409185
• Journal Information: Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 252:1; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION
ADRENAL HORMONES
ADRENALINE
ALKALI METAL COMPOUNDS
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CALCIUM 36
CALCIUM ISOTOPES
CARDIOTONICS
CARDIOVASCULAR AGENTS
CATIONS
CHARGED PARTICLES
DIFFUSION
DIGESTIVE SYSTEM
DOSE-RESPONSE RELATIONSHIPS
DRUGS
EVEN-EVEN NUCLEI
GASTROINTESTINAL TRACT
HORMONES
INHIBITION
INTESTINAL ABSORPTION
INTESTINES
IONS
ISOTOPES
KINETICS
LARGE INTESTINE
LIGHT NUCLEI
LITHIUM COMPOUNDS
MALES
MAMMALS
MEMBRANE TRANSPORT
NEUROREGULATORS
NUCLEI
ODD-ODD NUCLEI
ORGANS
RABBITS
RADIOISOTOPES
REACTION KINETICS
SODIUM 22
SODIUM ISOTOPES
STEROID HORMONES
SYMPATHOMIMETICS
UPTAKE
VERTEBRATES
YEARS LIVING RADIOISOTOPES