Alloxan effects on mitochondria: study of oxygen consumption, fluxes of Mg2+, Ca2+, K+ and adenine nucleotides, membrane potential and volume change in vitro

Abstract

Summary. Isolated mouse liver mitochondria incubated with alloxan showed stimulated resting (state 4) respiration with succinate, and inhibited resting respiration with pyridinelinked substrates, whereas active (state 3) respiration was decreased with both kinds of substrates. The effects were dependent on the concentration of alloxan, on the energy state, and on transport of inorganic phosphate and uptake of Ca 2+. Using succinate as substrate, the effects of alloxan on endogenous Mg 2+, K + and adenine nucleotides, uptake of K +, accumulated Ca 2+, membrane potential and volume were studied in liver mitochondria, and in addition efflux of endogenous K + and accumulated Ca 2+ were investigated in mouse islet mitochondria. High concentrations of alloxan (> 3 mmol/1) induced efflux of endogenous Mg 2+, K + and adenine nucleotides, effiux of accumulated Ca 2+, inhibition of uptake of K +, loss of membrane potential, and swelling. Low concentrations of alloxan (< 3 mmol/1) had similar effects only in the presence of added Ca 2+ and inorganic phosphate. The influence of potentially protective agents was studied mainly with regard to alloxan induced swelling. Complete or partial protection was offered by antimycin A, malonate, La 3+, Ni 2+, ruthenium red, mersalyl and N-ethylmaleimide, suggesting requirement for energized transport of Ca 2+ and uptake of inorganic phosphate. The start of the respiratory changes, decrease of membrane potential and loss of MgZ+preceded the release of accumulated Ca 2+, which occurred in parallel with efflux of K + and swelling. The loss of Ca 2+ in association with swelling agrees with data previously obtained using qualitative and quantitative electron microscopy and X-ray microanalysis of islet fl cells from alloxan-treated mice. Since preceding studies in vivo have shown that alloxan passes across plasma membranes and is taken up in mitochondria of islet fl cells and hepatocytes, the combined data support the view that alloxan diabetes may be due to mitochondrial damage.

Pharmacologic Modification of Subretinal Fluid Absorption in the Rabbit Eye

“…We investigated allox¬ an for this reason, since in certain experimental systems it can block the actions of c-AMP. 16 However, under the conditions of our experiments, it had no demonstrable effect on subret¬ inal fluid résorption. We found that c-GMP did facilitate subretinal fluid résorption, and future studies will be aimed at finding more specific and potentially clinically applicable means of causing this effect.…”

Hydrogen Peroxide Induces Intracellular Calcium Overload by Activation of a Non-selective Cation Channel in an Insulin-secreting Cell Line

“…This effectively negates the possibility that H 2 O 2 stimulated calcium release from either inositol 1,4,5-trisphosphate-sensitive or calcium-induced endoplasmic reticulum stores. The possibility that other intracellular organelles, in particular the nucleus (41) or mitochondria (42,43) -induced (10 mM) cell depolarization. Initially, the current was linear with a reversal potential near Ϫ40 mV (q), and following dialysis of the cell with an ATP-free solution (E), the current dramatically increased, and the reversal potential shifted more negative, indicating activation of the K ATP current.…”

Apoptosis and Mitochondrial Damage in INS-1 Cells Treated with Alloxan.

“…Other workers demonstrated that alloxan treatment damaged the mitochondrial function. 17,18) More recent, evidence has accumulated which supports a direct role for mitochondria in the process of apoptotic cell death. 14,15,39) In particular, the collapse of Dy and the release of cytochrome c have been recognized as one of the early events of apoptosis.…”

“…14,15) Release of cytochrome c and apoptosis induced factor from mitochondria into cytoplasm during mitochondrial permeability transition cause to active caspase family, leading to the completion of apoptosis. 15,16) Isolated liver mitochondria incubated with alloxan alters respiration, decreases in the concentration of adenine nucleotides, causes Ca 2ϩ release, and changes in the Dy, 17,18) indicating that alloxan directly induces the mitochondrial damage. However, the relationship between diabetes, apoptosis and mitochondrial damage has remained elusive.…”