NDLI: Identification of two discrete states of energized mitochondria: Experiments on single mitochondria

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Electrogenic transport of sodium ions in cytoplasmic and extracellular ion access channels of Na$^{+}$,K$^{+}$-ATPase probed by admittance measurement technique

Electrostatic effects upon adsorption and desorption of polylysines on the surface of lipid membranes of different composition

The 16th International Chromosome Conference (16th ICC) Amsterdam, The Netherlands, August 25–29, 2007

Biochemistry (Moscow) Supplement Series A: Membrane and Cell Biology : Volume 2, Issue 1, March 2008

Biochemistry (Moscow) Supplement Series A: Membrane and Cell Biology : Volume 1

Identification of two discrete states of energized mitochondria: Experiments on single mitochondria

Content Provider	Springer Nature Link
Author	Yaguzhinsky, L. S. Vyshenskaya, T. V. Kretushev, A. V. Tychinsky, V. P.
Copyright Year	2008
Abstract	Dynamic phase microscopy was used to measure the refractivity of a single mitochondrion. Our previous studies showed that application of an electric potential to artificial and natural mitochondrial membranes sharply increases their refractivity. Under the conditions of proton pump activity, the refractivity of a single mitochondrion is 2 to 4 times higher than an average refractivity of deenergized mitochondria. This study demonstrates that the membrane potential of energized mitochondria varies depending on environmental conditions and is controlled by the mitochondrial osmoregulation system. The refractivity of energized mitochondria, i.e., the difference between the refraction indexes of a single mitochondrion and the medium, is 0.02 ± 0.01, i.e., several times lower than that of the energized mitochondria whose membranes bear an electric charge. Earlier it was shown that refractivity of model multilayer systems formed from purified natural lecithin depends linearly on the electric field strength. These data point to a relationship between the refractivity of a single mitochondrion and the membrane potential generated during operation of the proton pump. Under normal conditions (250 mOsm), the mitochondrion behaves as a dynamic system oscillating on a minute scale between two functional states with different values of the refractivity index and different membrane potentials. The transition time is 10–30 s; the lifetime of both states is several minutes. The histograms reflecting the distribution of refractivities of single energized mitochondria within a population (n = 20–30) revealed the presence of two independent peaks (fractions II and III) with average refractivity values of 0.05 ± 0.01 and 0.09 ± 0.01, respectively; these fractions correspond to two long-lived states of mitochondria. However, under hypotonic conditions (120 mOsm), only one (“static”) state was identified, in which oscillations were absent and the refractivity of the overall mitochondrial population does not exceed 0.05 ± 0.01 (fraction II). Studies on mitoplast showed that values of refractivity are related to the inner mitochondrial membrane. It is inferred from these data that there exist two discrete states of mitochondria. Analysis of low-amplitude fluctuations of the refractivity of single mitochondria revealed the presence of frequency components at 1–3 Hz, presumably generated in response to non-uniform functioning of mitochondrial proton pumps. It is suggested that frequency components at 1.8-2.6 Hz are more characteristic of the ATPase pump, while the 1–1.3 Hz frequencies predominate during the functioning of respiratory proton pumps.
Starting Page	144
Ending Page	149
Page Count	6
File Format	PDF
ISSN	19907478
Journal	Biochemistry (Moscow) Supplement Series A: Membrane and Cell Biology
Volume Number	2
Issue Number	2
e-ISSN	19907494
Language	English
Publisher	SP MAIK Nauka/Interperiodica
Publisher Date	2008-07-27
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Cell Biology
Content Type	Text
Resource Type	Article
Subject	Cell Biology Biochemistry Biophysics

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