Glucagon effects on the membrane potential and calcium uptake rate of rat liver mitochondria
It has been widely reported that the in vivo administration of glucagon to rats results in the stimulation of calcium influx in subsequently isolated liver mitochondria. The mechanism of this effect is investigated through simultaneous measurements of calcium uptake rate and mitochondrial membrane potential. This allows the measurement of the calcium uniporter conductance independent of hormonal effects on electron transport or respiration. Two experimental approaches are used. The first involves measuring the uptake of 40-50 nmol of Ca/sup 2 +//mg of mitochondrial protein with the calcium dye antipyrylazo III; the second uses /sup 45/Ca/sup 2 +/ to follow uptake in the presence of 0.5 to 1.5 ..mu..M free calcium, buffered with HEDTA. In both cases a tetraphenyl phosphonium electrode is used to follow membrane potential, and membrane potential is varied using either malonate or butylmalonate in the presence of rotenone. The relative merits of these two approaches are discussed. The conductance of the calcium uniporter is found not to be stimulated by glucagon pretreatment. Also, the relative glucagon stimulation of both calcium influx and membrane potential is found to increase with increasing malonate concentration. These results imply that there is no direct stimulation of calcium uptake into liver mitochondria following glucagon treatment. The results are consistent with a glucagon stimulation of substrate transport, substrate oxidation, or a stimulation of electron transport resulting in an increased membrane potential and secondary stimulation of calcium uptake.
- Research Organization:
- Univ. of Rochester, NY
- DOE Contract Number:
- AC02-76EV03490
- OSTI ID:
- 5205341
- Journal Information:
- J. Biol. Chem.; (United States), Vol. 259:15
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCIUM 45
MEMBRANE TRANSPORT
CALCIUM COMPOUNDS
GLYCOGEN
BIOLOGICAL EFFECTS
ELECTRIC POTENTIAL
LIVER
MITOCHONDRIA
RATS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
CARBOHYDRATES
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DIGESTIVE SYSTEM
EVEN-ODD NUCLEI
GLANDS
INTERMEDIATE MASS NUCLEI
ISOTOPES
MAMMALS
NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
ORGANS
POLYSACCHARIDES
RADIOISOTOPES
RODENTS
SACCHARIDES
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics