Dimethyl sulfoxide: interactions with aromatic hydrocarbons.

Dimethyl sulfoxide (DMSO) enhanced the hypertaurinuria produced by benzene, chlorobenzene, and toluene in rats. Undiluted DMSO was more effective than DMSO diluted with water in potentiating the toxicity of benzene in both rats and mice. Supernatants (9000g) prepared from livers of rats treated with DMSO 24 hours earlier metabolized more benzene than those from control rats.

Arachidonic acid causes sudden death in rabbits.

Injection of sodium arachidonate (1.4 milligrams per kilogram) into the marginal ear veins of rabbits caused death within 3 minutes. Histological examination showed platelet thrombi in the microvasculature of the lungs. Rabbits were protected from the lethal effects of arachidonic acid by pretreatment with aspirin. Fatty acids closely related to arachidonic acid did not cause death.

Formation of an intermediate in prostaglandin biosynthesis and its association with the platelet release reaction.

A compound that could be converted to prostaglandin F(2alpha) by mild chemical reduction was formed by human platelets in response to arachidonic acid, collagen, or L-epinephrine. It was present in maximal amounts at about 1 min after addition of arachidonic acid or collagen to platelet-rich plasma. Its initial formation appeared to precede platelet aggregation by these agents and was closely correlated with the release of adenine nucleotides and radioactive 5-hydroxytryptamine from platelets. Moreover, the compound was itself found outside the platelets. This compound is probably an endoperoxide intermediate in prostaglandin biosynthesis and may be a trigger for the platelet release reaction.

Formation of prostaglandins during the aggregation of human blood platelets.

Prostaglandins E(2) and F(2alpha) were formed in response to ADP, L-epinephrine, or collagen by human platelets suspended in plasma containing citrate anticoagulant and stirred at 37 degrees C. The prostaglandins formed by platelets in response to collagen were rapidly released and the amounts formed were proportional to the amount of collagen added. The formation of the prostaglandins was associated with the single wave of aggregation induced by collagen or the second wave of aggregation induced by epinephrine. The above findings are discussed with reference to published studies on the biochemical changes occurring during platelet aggregation. It is suggested that the formation and release of prostaglandins is associated with the secretion of endogenous ADP and 5-hydroxytryptamine.

Fatty acids and the initial events of endothelial damage seen by scanning and transmission electron microscopy.

A method was developed for observing changes in the endothelial cells in rabbit ear veins in vivo by scanning electron microscopy. Injection of fatty acids into the ear vein caused damage to the endothelium. The first signs of damage seen were marked bulges in the nuclei and loss of the rhomboidal shape of the endothelial cells. More severe damage included loss of nuclei, leaving holes in the cytoplasm. Some parts of the damaged endothelium showed complete separation of cells from each other and exposure of sub-endothelial tissue to which platelets with pseudopodia were adhering. Damage to the endothelium was produced by arachidonic, linoleic, gamma-linolenic, 8,11,14-eicosatrienoic, 5,8,11,14,-eicosatetraenoic or 15-hydroperoxy-5,8,11,13-eicosatetraenoic acids. The effect of arachidonic acid was not prevented by pre-treating the animals with aspirin. It appears that damage produced by the fatty acids is non-specific.

The use of ferrokinetics in the study of experimental anemia.

Erythropoietic cells in bone marrow are vulnerable to cytotoxic substances. There are three types of erythroid precursors: cells that can take up Fe but do not proliferate (reticulocytes), those that can take up Fe and proliferate (normoblasts and pronormoblasts), and those cells that do not take up Fe but can proliferate and differentiate into the erythroid cell line (ERC and stem cells). Each of these erythroid precursors requires a certain time before they emerge into the peripheral blood as mature red blood cells. By applying our understanding of ferrokinetics associated with erythropoiesis, it was possible to estimate a cytotoxic effect of chemicals on proliferating erythgroid precursors (pronormoblasts) in mice by measuring 24-hr 59Fe uptake in red blood cells 48 hr after treatment with chemicals. The effect of chemicals on pluripotent hemopoietic stem cells in mice was also estimated by measuring 24-hr 59Fe uptake 72 hr after treatment with chemicals. The validity of experimental schemes was tested using cytarabine, methotrexate, vinblastine, cyclophosphamide, and busulfan, which are known to act against specific cell types. Effects on pluripotent hemopoietic stem cells were tested with or without activation of stem cells in G0 into cell cycle. Applications of the 59Fe uptake method in the study of (1) benzene toxicity and (2) effect of pentobarbital on the toxic action of hydroxyurea and cytarabine are described. Proper application of the ferrokinetic characteristics of erythropoietic cells enables the establishment of a methodology which can be used to evaluate potential toxic effects of chemicals on erythroid precursor cells and pluripotent hemopoietic stem cells.

Biological effects of the metabolites of dimethyl sulfoxide.

In summary, the effects of dimethyl sulfoxide (DMSO) and its metabolites, dimethyl sulfone (DMSO2) and dimethyl sulfide (DMS), were studied in five selected systems in rats and mice. DMSO enhanced the taurine excretion and the lethality produced by such aromatic hydrocarbons as benzene and chlorobenzene in rats. In mice, DMSO decreased the toxicity such cholinesterase inhibitors as paraoxon and octamethyl pyrophosphoramide. DMSO also lowered the body temperture of rats and reduced the motor activity of mice. Although DMSO2, the major metabolite of DMSO, was not effective in increasing the lethality of solvent hydrocarbons, it seemed to be quite as effective with respect to the other effects. DMS, although quite potent with respect to lowering body temperature and reducing motor activity, was relatively ineffective otherwise. Thus each of the metabolites has a spectrum of activity different from the parent compound; DMSO has the widest spectrum and DMS the narrowest. It remains to be determined whether the therapeutic effects of DMSO are related to the experimental effects reported above in animals, and whether DMSO2 and DMS may share any of the therapeutic effects of DMSO.

Metabolism of salicylate by isolated kidney and liver mitochondria.

Mitochondria are known to contain a P-450 like system similar to that found in microsomes. Since previous in vivo studies from this laboratory have suggested that renal mitochondria may metabolize salicylate (SAL) to a reactive intermediate capable of protein binding, the ability of isolated kidney and liver mitochondria to activate salicylate was investigated. Renal mitochondria were 4 times more active than liver in converting SAL to a reactive intermediate and metabolized approx. 1% of the SAL to 2,3-dihydroxybenzoic acid, the catechol analogue of SAL. The formation of 2,3-dihydroxybenzoate (2,3-DHBA) and the amount of radiolabel bound to mitochondrial protein was decreased in the presence of SKF 525-A; however, excess unlabeled metabolite had no effect on binding. These data indicate that kidney mitochondria activate SAL via a cytochrome P-450 like system, but suggest that the binding species is not 2,3-DHBA itself. Oxidation of SAL and covalent binding of radiolabel, however, were also observed after the addition of ferrous iron and ascorbic acid to a model system containing [14C]SAL and bovine serum albumin. Mannitol decreased SAL oxidation and covalent binding, suggesting radical formation may represent a non-enzymatic mechanism for SAL activation.

Acute toxicity and urinary excretion of diphenyldiselenide.

The acute toxicity of diphenyldiselenide (DPDS) in the male Swiss mouse was found to be enhanced by pretreatment with phenobarbital of SKF-525A. DPDS decreased hepatic glutathione content by 50% at 1 h after administration. Following administration of 14C-DPDS, labelled metabolites were found in urine but not in bile or feces. Analysis of the urinary metabolites of 14C-DPDS showed that selenium-containing metabolites elute from a DEAE-Sephadex column in two fractions: the first has not been chemically characterized, while the second peak contained the glucuronide conjugates of C6H4(OH)SeH and C6H5SeH. Virtually all of the administered selenium is excreted within 5 days, while only about 36% of the 14C is excreted in the same time period. This discrepancy indicates metabolic scission of the carbon-selenium bond.

The effect of age on salicylate-induced nephrotoxicity in male rats.

The administration of 500 mg/kg sodium [14C]salicylate to 3- and 12-month-old male rats produced proximal tubular necrosis in the older animals but only mild nonspecific cellular changes in the younger group. The onset of renal damage was similar for both 3- and 12-month-old rats but recovery time was prolonged in the older rats. Covalent binding of salicylate equivalents was present in renal cortices from all rats and was largely confined to the mitochondrial fraction; however, older rats displayed five times more binding to this organelle than younger rats. Also the mitochondrial pathway for salicylurate synthesis was significantly inhibited in the older animals. These results demonstrate the existence of an age-dependent susceptibility to salicylate nephrotoxicity and suggest that mitochondrial injury may play an important role in the development of salicylate-induced proximal tubular necrosis.