Abstract
Aim of this dissertation was to develop substances that are capable to increase the intracellular concentration of cyclic Guanosinmonophpsphate (cGMP). In thrombocytes an increase in cGMP leads to reduced aggregatibility.
Structural similarities between YC-1, an activator of soluble guanylyl cyclase, and MY 5445, an inhibitor of Phosphodiesterase, led to the development of a working model. This model was to describe substances which modulate the activity of the above enzymes in the desired manner. This promises a synergistic, cGMP-raising, effect.
According to our working model I synthesized N1-substituted 4-Aryl(-alkyl)-1-phthalazineamines, 4-Aryl(-alkyl)-1(2H)-phthalazinones substituted in position 2, amides of the 3-Arylalky-(4-oxo-3,4-dihydrophthalazin-1-yl)-acetic acid and N3-substituted 6-Phenyl-3-pyridazineamines.
Using the Born-Test many compounds were shown to inhibit the collagen-induced platelet aggregation in vitro. The most pronounced effects were found for the Phthalazineamines and some 1(2H)-Phthalazinones. Usually the 4-Aryl-compounds were found to have an IC50 which was lowered by a factor of 2, compared with the corresponding 4-Arylalkyl-compounds. A substitution in the aryl-moiety leads to a decrease in activity, too. The most suitable substituents at N1 were the following: omega-Imidazol-1-yl-alkyl, omega-Triazol-1-yl-alkyl, omega-Dialkylamino-alkyl, 2-(2-Hydroxyethyl)ethoxy, and Furan-2-yl-methyl. The optimal length of the alkyl-chain could be demonstrated to be four methylene-groups for the Imidazole- and Triazole-compounds.
Using collagen as inducer, the lowest IC50 found was 8.4 microM for the N-[4-(1H-1,2,4-Triazol-1-yl)butyl]-4-phenyl-1-phthalazinamine. When serotonine is used to start the aggregation the lowest IC50 is 2.5 microM for the N-(Furan-2-yl-methyl)-4-phenyl-1-pthtalazinamine (collagen : 28 microM ). In a rat-tail-model this compound is a non-competitive antagonist of the 5-HT2A-receptor.
A selection of in vitro effective substances was also tested for inhibition of PDE 5 and activation of sGC. The N-(Furan-2-yl-methyl)-4-phenyl- and the N-(Furan-2-yl-methyl)-4-phenylmethyl-1-pthtalazinamine both have an IC50 for PDE 5 of 10 microM. In addition, the N-(Furan-2-yl-methyl)-4-phenyl-1-pthtalazinamine was found to activate the sGC by factor 5 when present in a concentration of 100 microM. This proves that the model is capable of describing substances with PDE 5 inhibiting and sGC activating effects.
By use of a Laser-Thrombosis-Model some selected compounds were tested for antithrombotic effects in vivo. The most effective compound was the N-[5-(1H-1,2,4-Triazol-1-yl)pentyl]-4-phenyl-1-phthalazinamine. 2 h after peroral application (60 mg/kg) it reduced the formation of thrombi in arterioles by 12 % and venoles by 7 %. |
