The effect of lipoic acid administration on the urinary excretion of thiocyanate in rats exposed to potassium cyanide

The oxidation of cyanide (CN-) to a much less toxic thiocyanate (SCN-) is the main in vivo biochemical pathway for CN- detoxification. SCN- is excreted mainly in urine. This study was performed to investigate the effect of lipoic acid (LA) on the urinary excretion of thiocyanate (SCN- ; rhodanate) in rats. Groups of the animals were treated intraperitoneally (i.p.) as follows: group 1: potassium cyanide (KCN) (1 mg/kg); group 2: KCN (1 mg/kg) + LA (100 mg/kg). Urine was collected for 24 h and the pooled samples were examined for SCN- levels. The obtained results indicated that the treatment of animals with potassium cyanide and LA in combination significantly increased the urinary excretion of SCN- in comparison w ith the respective values in the KCN-alone-treated group. It indicates that LA increased the rate of CN- detoxification in rats

Lipoic acid as a possible pharmacological source of hydrogen sulfide/sulfane sulfur

The aim of the present study was to verify whether lipoic acid (LA) itself is a source of H2S and sulfane sulfur. It was investigated in vitro non-enzymatically and enzymatically (in the presence of rat tissue homogenate). The results indicate that both H2S and sulfane sulfur are formed from LA non-enzymatically in the presence of environmental light. These results suggest that H2S is the first product of non-enzymatic light-dependent decomposition of LA that is, probably, next oxidized to sulfane sulfur-containing compound(s). The study performed in the presence of rat liver and kidney homogenate revealed an increase of H2S level in samples containing LA and its reduced form dihydrolipoic acid (DHLA). It was accompanied by a decrease in sulfane sulfur level. It seems that, in these conditions, DHLA acts as a reducing agent that releases H2S from an endogenous pool of sulfane sulfur compounds present in tissues. Simultaneously, it means that exogenous LA cannot be a direct donor of H2S/sulfane sulfur in animal tissues. The present study is an initial approach to the question whether LA itself is a donor of H2S/sulfane sulfur

Hypotensive effect of alpha-lipoic acid after a single administration in rats

Objective: The effect of alpha-lipoic acid on blood pressure was investigated many times in chronic studies, but there are no studies on the effect of this compound after a single administration. Alpha-lipoic acid is a drug used in diabetic neuropathy, often in obese patients, to treat hypertension. Therefore, knowledge of the potential antihypertensive effect of alpha-lipoic acid even after a single dose and possibly too much pressure reduction is interesting and useful. Methods: The mechanism of the hypotensive effect of alpha-lipoic acid was examined in normotensive rats in vivo after a single intraperitoneal administration, blood pressure in the left carotid artery of the rats was measured prior to the administration of the compounds (alphalipoic acid and/or glibenclamide) and 80 min thereafter. Results: Alpha-lipoic acid at a dosage of 50 mg/kg b.w. i.p. significantly decreased the blood pressure from the 50th min after drug administration. This cardiovascular effect of this compound was reversed by glibenclamide, a selective KATP blocker. Glibenclamide alone at this dose did not significantly affect the blood pressure. Statistical significance was evaluated using two-way ANOVA. Conclusion: This suggests that alpha-lipoic acid affects ATP-dependent potassium channels. It is possible that this is an indirect effect of hydrogen sulfide because alpha-lipoic acid can increase its concentration. The results obtained in this study are very important because the patients taking alpha-lipoic acid may be treated for co-existing hypertension. Therefore, the possibility of blood pressure lowering by alphalipoic acid should be taken into account, although it does not lead to excessive orthostatic hypotension. (Anatol Cardiol 2016; 16: 306-9

Inactivation of aldehyde dehydrogenase by nitroglycerin in the presence and absence of lipoic acid and dihydrolipoic acid : implications for the problem of differential effects of lipoic acid "in vitro" and "in vivo"

Lipoic acid (LA-(SS), LA) and its reduced form - dihydrolipoic acid DHLA-(SH)2, DHLA) are synthesized mainly in the mammalian liver. In this study, we investigated in vitro the inactivation of yeast aldehyde dehydrogenase (ALDH) by nitroglycerin (GTN) in the presence and absence of LA and DHLA. In vivo studies were performed to answer the question whether LA administered jointly with GTN for 8 days will affect the ALDH activity in the rat liver. The results indicated that in vitro both LA and DHLA restored and protected ALDH activity against GTN-induced inactivation, while treatment of rats with LA and GTN in combination did not provide any protection against GTN-induced ALDH inhibition. In summary, the obtained results seem to confirm earlier reports indicating the differential effects of LA in vitro and in vivo