H sup + -dependent calcium uptake into an IP sub 3 -sensitive calcium pool from rat parotid gland

Journal Article · Sat Oct 01 00:00:00 EDT 1988 · American Journal of Physiology; (USA)

OSTI ID:6289829

Thevenod, F; Schulz, I ^[1]

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1. Max-Planck-Institut fuer Biophysik, Frankfurt (West Germany)

In permeabilized parotid cells and in isolated membrane vesicles from parotid endoplasmic reticulum (ER), Mg-ATP-dependent Ca{sup 2+} uptake was measured using a Ca{sup 2+}-specific macroelectrode and {sup 45}Ca{sup 2+}, respectively. Mg-ATP-dependent Ca{sup 2+} uptake was inhibited by vanadate by {approximately}45% in permeabilized cells and by {approximately}70% in membrane vesicles from ER during the initial 10 min. After this lag phase, Ca{sup 2+} uptake increased. Subsequent addition of inositol 1,4,5-trisphosphate (IP{sub 3}) caused a similar Ca{sup 2+} release compared with control. This indicates that in presence of vanadate an IP{sub 3}-sensitive Ca{sup 2+} pool was filled. However, when protonophores, such as nigericin or carbonyl cyanide-m-chlorophenylhydrazone, were added in addition to vanadate, this low steady-state free (Ca{sup 2+}) was not reached. {sup 45}Ca{sup 2+} uptake was reduced by {approximately}70% within 60 min, and IP{sub 3} did not cause {sup 45}Ca{sup 2+} release when given subsequently, indicating that filling of an IP{sub 3}-sensitive Ca{sup 2+} pool was prevented. Mg-ATP-driven H{sup +} uptake into ER vesicles was abolished by protonophores and by the H{sup +}-ATPase blockers N-ethylmaleimide and Dio 9 but was unaltered by vanadate. Preincubation of ER vesicles in a medium without Ca{sup 2+}, but with vanadate and with Mg-ATP to generate an H{sup +} gradient, allowed demonstration of {sup 45}Ca{sup 2+} uptake from a medium that did not contain ATP. The data indicate that both a Ca{sup 2+} and a H{sup +} pump are located in a compartment of ER that is also sensitive to IP{sub 3}. Ca{sup 2+} uptake is coupled to an H{sup +} gradient that is generated by the H{sup +} pump and most likely occurs via Mg-ATP-driven Ca{sup 2+}-H{sup +} countertransport but to some extent can also operate in absence of ATP at the expense of the H{sup +} gradient.

• OSTI ID: 6289829
• Journal Information: American Journal of Physiology; (USA), Vol. 255:4; ISSN 0002-9513
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ATP-ASE
BIOCHEMISTRY
CALCIUM 45
UPTAKE
ENZYME INHIBITORS
BIOLOGICAL EFFECTS
ATP
CALCIUM CHLORIDES
CENTRIFUGATION
ENDOPLASMIC RETICULUM
MAGNESIUM COMPOUNDS
PROTONS
RATS
SALIVARY GLANDS
VANADATES
ACID ANHYDRASES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM COMPOUNDS
CALCIUM HALIDES
CALCIUM ISOTOPES
CELL CONSTITUENTS
CHEMISTRY
CHLORIDES
CHLORINE COMPOUNDS
DAYS LIVING RADIOISOTOPES
ELEMENTARY PARTICLES
ENZYMES
EVEN-ODD NUCLEI
FERMIONS
GLANDS
HADRONS
HALIDES
HALOGEN COMPOUNDS
HYDROLASES
INTERMEDIATE MASS NUCLEI
ISOTOPES
MAMMALS
NUCLEI
NUCLEONS
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
OXYGEN COMPOUNDS
PHOSPHOHYDROLASES
RADIOISOTOPES
RODENTS
SEPARATION PROCESSES
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques