Modulation of agonist-activated calcium influx by extracellular pH in rat pancreatic acini

Journal Article · Fri Dec 01 04:00:00 EST 1989 · American Journal of Physiology; (USA)

OSTI ID:6983957

Muallem, S; Pandol, S J; Beeker, T G ^[1]

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1. Univ. of Texas Southwestern Medical Center, Dallas (USA)

The biochemical and Ca2+ transport pathways involved in generating the hormone-evoked Ca2+ signal are reported to be influenced by pH. The present study was designed to determine the effect of extracellular pH (pHo) and intracellular pH (pHi) on hormone-stimulated Ca2+ transport. We used rat pancreatic acini and measured free cytosolic Ca2+ concentration ((Ca2+)i) with fura-2, pHi with 2,7-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF), and Ca2+ fluxes with 45Ca2+. In the presence of external Ca2+, increasing pHo increased steady-state (Ca2+)i during sustained agonist stimulation; in the absence of external Ca2+, this increase in (Ca2+)i did not occur. The addition of an antagonist or blocking plasma membrane Ca2+ influx with La3+ in stimulated cells suspended at pHo 8.2 resulted in a reduction in (Ca2+)i. Increasing pHo increased the rate and extent of 45Ca2+ uptake into stimulated cells and the rate and extent of Ca2+ reloading of intracellular stores. The increased Ca2+ content of the intracellular stores with increased pHo indicated that at physiological pHo and pHi the agonist-mobilizable internal stores are not saturated with Ca2+. Changes in pHo affected pHi. However, changes in pHi at constant pHo had no effect on hormone-evoked (Ca2+)i increase, reduction in (Ca2+)i after hormone stimulation, or reloading of intracellular stores. We conclude that the hormone-activated plasma membrane Ca2+ entry pathway responsible for Ca2+ reloading is directly modulated by external H+.

• OSTI ID: 6983957
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 257; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
AROMATICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL PATHWAYS
BODY
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CELL MEMBRANES
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
DYES
ENDOCRINE GLANDS
EVEN-ODD NUCLEI
FLUORESCEIN
GLANDS
HORMONES
HYDROXY ACIDS
HYDROXY COMPOUNDS
IN VITRO
INTERMEDIATE MASS NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
LANTHANUM COMPOUNDS
MAMMALS
MEMBRANE TRANSPORT
MEMBRANES
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PANCREAS
PH VALUE
PHENOLS
POLYPHENOLS
RADIOISOTOPES
RARE EARTH COMPOUNDS
RATS
RODENTS
STEADY-STATE CONDITIONS
TRACER TECHNIQUES
VERTEBRATES