F. Sandoval

Ultrastructural changes of tissues produced by inhalation of thinner in rats

Thinner is a substance that is used for industrial purposes and for drug abuse; addiction is of young people (average age, 7.5 years). Although the health problem of voluntary or nonvoluntary solvent sniffing is important, great attention has been paid to the epidemiology and pharmacology of paint thinner or industrial solvents inhalation, but studies at the morphological and biochemical level are scarce. This work describes the morphological changes in the lung, liver, kidney, adrenal glands, and central nervous system induced by short‐ (up to 4 weeks) and long‐term (up to 14 weeks) periods of thinner inhalation in rats. Microsc. Res. Tech. 40:56–62, 1998.

On the locus of action of Na+ at site I of oxidative phosphorylation

The effect of octylguanidine on the Na+ stimulated oxygen uptake of rat liver mitochondria and bovine heart submitochondrial particles and on the Na+ induced efflux of K from the mitochondria has been examined. The results indicate that the action of Na+ is inhibited by octylguanidine, but that the degree of inhibition depends on the concentration of the cation. Apparently, a competition exists between Na+ and octylguanidine for a common site. Octylguanidine, but not oligomycin, at certain concentrations restores in mitochondria incubated with Na+ the capacity to respond to uncouplers. A competitive effect between monovalent cations and octylguanidine has been observed in submitochondrial particles oxidizing NADH.

Dependency of the ATPase and 32P—ATP exchange reaction of mitochondria on K+ and electron transport

Abstract The 2,4-dinitrophenol-stimulated ATPase activity and the 32 P-ATP exchange reaction has been studied in rat liver mitochondria having less than 15 nmoles of K + per milligram of protein. With 200 m m sucrose in the incubation media, the permeation of K + and an oxidizable substrate is required for maximal stimulation of ATPase activity by 2,4-dinitrophenol. In these conditions, the 2,4-dinitrophenol-stimulated ATPase is inhibited by antimycin, acetate and mersalyl and depends to a certain extent on the rate of electron transport. The 32 P-ATP exchange reaction of mitochondria with a low content of K + also requires K + permeation and is inhibited by antimycin, cyanide, 2,4-dinitrophenol, and acetate. The results suggest that the entrance of ATP into the mitochondria is compulsory linked to K + uptake in a process that depends on a negative internal potential.

Dependency of the 2,4-dinitrophenol stimulated ATPase activity on K + and respiration.

Abstract The 2,4-dinitrophenol (DNP) stimulated ATPase activity has been studied in rat liver mitochondria which have a K+ content of 15 mM or less. It has been found that in these mitochondria the ATPase activity becomes strictly dependent on K+ and on electron transport. The activity reaches a maximum with 20 mM KCl and is inhibited by rotenone and antimycin. Succinate, in some experiments, enhances the DNP stimulated ATPase activity in a malonate sensitive process.

Guanidine sensitive transport of Na+ and K+ in mitochondria

Abstract Na + induce the release of K + from mitochondria through a process that is accompanied by a high respiratory rate. With succinate as substrate, octylguanidine, an inhibitor of oxidative phosphorylation at Site I, blocks the Na stimulated oxygen uptake and the Na + induced release of K + . These findings indicate that mitochondria have a guanidine sensitive system that is involved in the translocation of Na + and K + .

K+ independent action of valinomycin in mitochondria

Abstract Some of the effects of valinomycin on mitochondria incubated in an all sodium medium have been studied. The 2,4-dinitrophetiol-stimulated adenosinetriphosphatase activity is inhibited by valinomycin. Maximum inhibition is obtained at pH 7.0. The inhibition depends on the concentration of NaCl in the mixture and on the concentration of the antibiotic. Mitochondrial oxygen uptake stimulated by 2,4-dinitrophenol is depressed by valinomycin with glutamate, malate-pyruvate, α-ketoglutarate, and succinate as substrates in the absence of added inorganic phosphate. Inorganic phosphate reverses the inhibition produced by valinomycin of the 2,4-dinitrophenol-stimulated oxygen uptake of mitochondria oxidizing glutamate, but inorganic phosphate has no effect on the inhibition produced by valinomycin on the 2,4-dinitrophenol stimulated oxygen uptake with α-ketoglutarate as substrate. In the case of malate-pyruvate, 0.01 m inorganic phosphate produces abiphasic response in which initially oxygen uptake is depressed but later it is not affected. Acetate does not reverse the inhibition produced by valinomycin in the 2,4-dinitrophenol stimulated oxygen uptake with any of the substrates assayed. In the absence of added K + , valinomycin does not affect coupled respiration nor oxidative phosphorylation in an all sodium medium.