Effects of diltiazem on the calcium accumulation and ATP synthesis simultaneously sustained by isolated rat heart mitochondria.

1. The effects of diltiazem have been investigated in isolated rat heart mitochondria exposed to conditions possibly attained in ischemia-damaged cells. 2. The results obtained indicate that diltiazem, at the concentrations expected within cells following pharmacological treatment, does not significantly affect the mitochondrial calcium content. 3. Diltiazem did not appear to modify ATP synthesis, and hence the capacity of mitochondria to sustain the ATP-requiring processes needed for the recovery of cardiac cells.

Effects of diltiazem on liver mitochondria of rats: a reconsideration.

1. The effects of the Ca-channel blocker diltiazem (a drug of the benzothiazepine family) on bioenergetic metabolism have been assessed on isolated rat liver mitochondria. 2. Millimolar concentrations of diltiazem induced a decrease of both the ADP- and the uncoupler-stimulated respiration and a concomitant slight increase of the resting respiration. 3. Under the same experimental conditions diltiazem decreased the transmembrane electrical potential while leaving calcium uptake unaffected. 4. Micromolar concentrations of diltiazem, which are close to therapeutic haematic levels, were without effect.

Biochemical and morphological observations on rat liver and kidneys six months after intravenous injection of a perfluorocompound emulsion.

The histological appearance of liver and kidneys and the energy metabolism of isolated liver and kidney mitochondria were evaluated in rats 6 months after intravenous administration of 1 ml of a perfluorocompound emulsion. Both liver and kidney specimens showed neither significant histological alteration nor the presence of intracytoplasmic perfluorocompound particles. A substantial depression of the rate of ATP synthesis was observed both in liver and kidney isolated mitochondria (with respect to control mitochondria) although the magnitude of the transmembrane electrical potential was unaltered. The depression of ATP synthesis in mitochondria isolated from perfluorocompound-treated rats appeared then unrelated to the presence of perfluorocompound micelles within the cells, and might result from the interaction of either the perfluorocompound or the emulsifying agent with the mitochondrial ATP synthetase.

Uncoupling effect of the general anesthetic 2,6-diisopropylphenol in isolated rat liver mitochondria.

2,6-Diisopropylphenol, a general anesthetic, was previously reported to reduce the transmembrane electrical potential in isolated rat liver mitochondria without affecting the rate of ATP production. This effect appeared to contrast with the generally accepted chemiosmotic mechanism for oxidative phosphorylation. In this study we further examined the influence of 2,6-diisopropylphenol on the production of ATP by isolated mitochondria and we studied its effect on the permeability of the inner mitochondrial membrane to protons. In order to clarify the effects of 2,6-diisopropylphenol on mitochondrial ATP production the activities of the adenine nucleotide translocator and the ATP synthetase were evaluated. The results obtained indicate that the depression of the transmembrane electrical potential elicited by 2,6-diisopropylphenol decreased the activity of the ATP synthetase (as expected in the chemiosmotic model for energy coupling), but not that of the adenine nucleotide translocator. The decrease of the ATP synthetase activity, however, did not result in an apparent inhibition of the overall rate of ATP production in isolated mitochondria due to the rate-limiting effect of the adenine nucleotide translocator in this process. Moreover 2,6-diisopropylphenol was found to increase the permeability to protons of the inner mitochondrial membrane; this effect became more marked as the pH of the incubation medium was increased, demonstrating that it involved the dissociated form of 2,6-diisopropylphenol. These observations suggested that 2,6-diisopropylphenol affected oxidative phosphorylation by acting as a mild protonophore and that its effectiveness was limited by the low fraction of phenol dissociated at near-physiological pH.

Influence of the anesthetic 2,6-diisopropylphenol on the oxidative phosphorylation of isolated rat liver mitochondria.

Isolated rat liver mitochondria have been incubated in the presence of the general anesthetic 2,6-diisopropylphenol (0-100 microM) and the efficiency of oxidative phosphorylation has been evaluated by measuring the respiratory rates, the rates of ATP synthesis or hydrolysis and the magnitude of the transmembrane electrical potential. The results obtained indicate that: (a) in mitochondria energized either by succinate or by ATP, 2,6-diisopropylphenol decreased the transmembrane electrical potential and increased the rates of either electron transfer or ATP hydrolysis; (b) in succinate-energized mitochondria 2,6-diisopropylphenol, at concentrations causing substantial depression of the transmembrane electrical potential, did not modify either the rate of phosphorylation of added ADP or the rate of ADP-stimulated respiration: (c) in succinate-energized mitochondria 2,6-diisopropylphenol caused a concentration-dependent inhibition of the uncoupler-stimulated rate of succinate oxidation. These findings suggest that under the experimental conditions reported 2,6-diisopropylphenol affected the generation and/or maintenance of the transmembrane electrical potential while leaving unchanged the coupling between the electron flow in the respiratory chain and the synthesis of ATP.

Techniques for experimental rat kidney (and liver) perfusion.

The technique described here allows to perfuse in situ either the left kidney alone, both kidneys or both kidneys and the liver of rats with few operations, without danger of organs damage and with a good control of temperature and pressure. This technique allows a good maintainance of the metabolic activity of the perfused tissues and offers the possibility to collect urine by cannulating the bladder.