Effects of aspirin and related drugs in vitamin E-deficient rats

Constitutive and heat-shock induced expression of Hsp70 mRNA during chicken testicular development and regression

The constitutive and heat shock induced expression of Hsp70 mRNA was investigated in normal adult chicken testis and in adult testis after testicular regression induced by diethylstilbestrol (DES) treatment. In addition to the canonical form of Hsp70 mRNA, we have detected transcripts with an extended 5'UTR and transcripts containing, in the 5'UTR, sequences of the 18S ribosomal RNA. Hsp70 was expressed in unstressed male gonads in adult and regressed testis, being the expression much lower in regressed testis. Upon heat shock at 44 degrees C or 46 degrees C, Hsp70 was highly induced in both tissues. However, when testicular seminiferous tubules were incubated at the chicken internal temperature of 39 degrees C, no induction of Hsp70 was observed in mature testis, while the expression markedly increased in regressed testis. Induction at 39 degrees C was completely inhibited in the presence of 6 mM aspirin. Aspirin in the range 3-10 mM decreases the expression of Hsp70 in unstressed and stressed testicular cells, in striking contrast with the effect observed in other tissues as liver. These data suggest that the expression of Hsp70 is regulated in a specific manner in chicken testis and particularly in the male gonad undergoing regression.

Oxidative stress and muscular dystrophy

Oxidative stress may be the fundamental basis of many of the structural, functional and biochemical changes characteristic of the inherited muscular dystrophies in animals and humans. The presence of by-products of oxidative damage, and the compensatory increases in cellular antioxidants, both indicate oxidative stress may be occurring in dystrophic muscle. Changes in the proportions and metabolism of cellular lipids, abnormal functions of cellular membranes, altered activity of membrane-bound enzymes such as the SR Ca2+-ATPase, disturbances in cellular protein turnover and energy production and a variety of other changes all indicate that these inherited muscular dystrophies appear more like the results of oxidative stress to muscle than any other type of underlying muscle disturbance. Particular details of these altered characteristics of dystrophic muscle, in combination with current knowledge on the processes of oxidative damage to cells, may provide some insight into the underlying biochemical defect responsible for the disease, as well as direct research towards the ultimate goal of an effective treatment.

Vitamin E and skeletal muscle

Vitamin E deficiency causes a myopathy in a number of animal species but the mechanism of the damage is obscure. The role of vitamin E in protecting skeletal muscle against exercise-induced damage has been investigated using both in situ and in vitro preparations. Muscles from vitamin E-deficient mice and rats were more prone than normal to damage during contractile activity; the tissue rather than the plasma level of the vitamin is probably the more important factor in this respect. Although vitamin E-deficient muscle was found to be more susceptible to peroxidative damage when stressed with iron and ascorbic acid, it was not possible to demonstrate that the damage occurring during contractile activity was mediated by free radicals.

Regulation of vascular prostaglandin synthesis by metabolites of arachidonic acid in perfused rabbit aorta

To address the hypothesis that metabolites of arachidonic acid are important regulators of prostaglandin (PG) synthesis in intact vascular tissue, we studied arachidonate metabolism in rabbit aortas in response to a continuous infusion of arachidonic acid, 10 micrograms/ml. Prostacyclin (PGI2; measured as 6-keto-PGF1 alpha) production rate accelerated during the first 2 min, reached peak velocity at 2 min, and then progressively decelerated. The velocity profile of PGI2 production was similar to that previously reported for cyclooxygenase holoenzyme assayed in vitro, and was consistent with progressive inactivation of the enzymes leading to PGI2 synthesis. We determined the specific inhibition of cyclooxygenase and prostacyclin synthetase by measuring PGI2 and PGE2 production rates and by infusing cyclic endoperoxides. Our results indicate preferential inactivation of cyclooxygenase during arachidonate metabolism, most likely due to cyclooxygenase-derived oxidative intermediates. This was a dose-dependent response and resulted in a progressive decrease in the 6-keto-PGF1 alpha/PGE2 ratio. Exogenously added 15-hydroperoxy eicosatetraenoic acid, on the other hand, actually stimulated cyclooxygenase activity at low doses, while markedly inhibiting prostacyclin synthetase. This finding, along with the accelerating nature of arachidonate metabolism, is consistent with the concept of "peroxide tone" as a mediator of cyclooxygenase activity in this system. These results demonstrate that arachidonate metabolites regulate PG synthesis in intact blood vessels. The progressive enzymatic inhibition intrinsic to arachidonate metabolism may be a model for similar changes occurring in states of enhanced lipid peroxidation. These metabolic alterations might greatly influence the numerous vascular functions known to involve arachidonic acid metabolism.

The effect of pretreatment with vitamin E on the effects of endotoxin in rat

Twenty male rats weighing about 100g were treated subcutaneously with 25 mg alpha-tocopherol acetate. The rats were given 0.4 mg/100 g endotoxin intraperitoneally 24 hrs after the pretreatment, and were sacrificed 18 hrs after the endotoxin injection. The lipid peroxide level as evaluated by the TBA-value remained at the no-treatment level. In a similar group of rats not pretreated but given the same dose of endotoxin intraperitoneally, the TBA-value rose significantly. There were no statistically significant differences in the mean plasma ALAT and OCT activities or in the mean liver or plasma Zn concentrations between the endotoxin treated groups. The plasma OCT and ALAT activities were significantly correlated with the liver TBA-values in both endotoxin-treated groups but the plasma Zn and OCT, or plasma Zn and ALAT were significantly correlated only in the group pretreated with vitamin E. In a control group of 20 animals not treated with either endotoxin or vitamin E the plasma Zn and vitamin E concentrations were statistically significantly (P less than 0.05) correlated. It is suggested that the endotoxin effect on the liver is probably mediated by prostaglandin-like substances.