Synthesis and inhibitory effect on platelet aggregation and antihypertensive activity of 1-hydroxy-2,5-dihydro-1H-imidazole-2-carboxylic acid 3-oxides, 1,3-dihydroxyimidazolidine-2-carboxylic acids, and 1,4-dihydroxy-2,3-piperazinediones.

The reaction of 1,2-hydroxylamino-oximes 1 with pyruvic or glyoxylic acid and of 1,2-bishydroxylamines 4 with glyoxylic acid resulted in 2,5-dihydro-1H-imidazole-2-carboxylic acid 3-oxides 2 and 2-imidazolidinecarboxylic acids 5, respectively. It was found that hydroxylamino acids 2 and 1,4-dihydroxy-2,3-piperazinediones 7 showed marked inhibitory effect on platelet aggregation. 1-Hydroxy-2-methyl-1,5,6,7,8,8a-hexahydro-2H,4H-cycloheptimidazole -2-carboxylic acid 3-oxide 2e exhibited antihypertensive activity.

Kinetics of nitric oxide liberation by 3,4-dihydro-1,2-diazete 1,2-dioxides and their vasodilatory properties in vitro and in vivo.

Derivatives of 3,4-dihydro-1,2-diazete 1,2-dioxides (DD) have been investigated as NO donors in vitro and in vivo. Using nitronylnitroxides as spin traps for NO, these compounds were shown to decompose in water solutions at physiological pH and temperature, producing two molecules of NO per one DD molecule. Rate constants of DD decomposition were found to be in the range from 10(-8) to 6.5 x 10(-7) c-1 in water and between 3 x 10(-7) and 1.6 x 10(-5) c-1 in dimethylsulfoxide. In vitro experiments performed with perfused rat tail artery showed that some of DD derivatives are highly effective vasodilators in concentrations from 5 to 80 microM while standard NO donor 3-(4-morpholino)-sydnonimine, SIN-1, does not lead to arterial vasodilation in these concentrations. Significant (up to 30%) decrease of systolic arterial blood pressure was observed in hereditary hypertensive rats (ISIAH-strain) when some of DD were injected intraperitoneally in doses 40-200 micrograms/kg b.w., while the same effect of trinitroglycerin, TNG, was found at much higher dose equal to 900 micrograms/kg b.w.

Derivatives of 1,2-diazetidine-1,2-di-N-oxides--a new class of soluble guanylate cyclase activators with vasodilatory properties.

Derivatives of diazetidine-di-N-oxides have been found capable of the nonenzymatic generation of nitric oxide by the principally new mechanism of the nitric oxide splitting at physiological pH values. The effect of the synthesized compounds on human platelet soluble guanylate cyclase activity as well as their spasmolytic and hypotensive action were studied. Four of 7 derivatives studied exhibited a distinct correlation between the ability of being decomposed with the nitric oxide formation, activation of soluble guanylate cyclase, and spasmolytic and antihypertensive activities. Among them, 3-brom, 4-methyl-3,4-tetramethylene-diazetidine-di-N-oxide has proved to be most effective, its spasmolytic effect being commensurable with glyceryl trinittrate activity. The revealed correlation allows us to regard 1,2-diazetidine-1,2-di-N-oxide derivatives as vasodilatory agents of a new class.

Quantitative determination of SH groups in low- and high-molecular-weight compounds by an electron spin resonance method.

To quantitatively determine SH groups in high- and low-molecular-weight compounds, a disulfide biradical (RS-SR), where R is imidazoline residue, has been used. The biradical is shown to participate in a thiol-disulfide exchange reaction with compounds containing SH groups. In this case the ESR spectra of the biradical RS-SR and the resulting monoradical R-SH are different. The reaction of the biradical with cysteine, glutathione, and human serum albumin has been studied using the ESR method and the rate constants kf of this reaction have been calculated. Studies of the pH dependence of kf indicate that the thiol-disulfide exchange occurs by reaction with mercaptidione. Protein human serum albumin and hemoglobin have been modified by RS-SR. It has been shown that the treatment of modified proteins with reduced glutathione leads to removal of the radical from the protein; such modifications are thus reversible. The method proposed has been used to quantitatively determine the SH groups of cysteine and glutathione in mouse and rat blood. The method is shown to coincide within experimental error with the determination of glutathione and cysteine by titration with p-chloromercuribenzoate or reaction with Ellman's reagent. This method allows detection of 10(-6)-10(-7) M SH compounds even in colored and highly absorbing samples. The kinetics of the SH group modification can also be determined, leading to deduction about accessibility of the SH group in protein.