Mitzi Maresca

THE EFFECT OF METHYLGLYOXAL ON THE GLYCOLYTIC ENZYMES

with free arginine and have found that the reaction rate, much faster with methylglyoxal than with phenylglyoxal, depends on the buffer type and increases by increasing the pH. Data on the inactivation mechanism of aldolase and glyceraldehyde-3-phosphate dehydrogenase by methyl- glyoxal have shown that one arginine residue is involved in the interaction of the enzyme with the ketoalde- hyde [S ,6].Since all glycolytic enzymes,except triose- phosphate isomerase, contain essential arginine resi- dues [7-l 11, it seemed worthwhile to compare the effect of methylglyoxal on the enzymes of the glyco- lytic pathway. 2. Materials and methods Substrates, enzymes and coenzymes were pur- chased from either Sigma or Boehringer Mannheim . Methylglyoxal (Fluka) freshly distilled and phenyl- glyoxal (Sigma), prepared every time before use were tested according to [ 121 and [ 131, respectively. Lactatt dehydrogenase (EC 1 .l .1.27) from rabbit muscle was assayed in the presence of 50 mM phosphate buffer (pH 7 .O), 3 .O mM pyruvate and 0.2 mM NADH; alco- hol dehydrogenase (EC 1 .l .l .l) and hexokinase (EC 2.7.1.1) from yeast were tested according to [14] and [

Synthesis and anti-platelet activity of some 2-(dialkylamino)chromones

Substituted 2-(diethylamino) or 2-(ethylamino)chromones 5a—g were obtained from the reaction of suitable phenols with the reagent ethyl N,N-diethyl- or N-ethylmalonamate/POCl3 (2a or 2b). The above compounds, together with other N-substituted 2-aminochromones, either prepared from related chromones by simple reactions (5h—k) or previously obtained by us (5l—w), were tested in vitro for their inhibitory activities against human platelet aggregation induced by collagen, ADP and arachidonic acid. Many compounds showed activity and some were more active than acetylsalicylic acid in the tests with ADP and arachidonic acid. When the 2-amino substituent of tested chromones was a diethylamino group, the highest activity was found. The presence in position 7 of electron releasing substituents (OH, OCH3, CH3) led to an increase of activity, whereas a decrease occurred when an electron withdrawing substituent was present in position 3 (NO2) or 6 (NO2, Cl).

Alkaline extraction and reverse-phase high-performance liquid chromatography of adenine and pyridine nucleotides in human platelets

The levels of adenine (ATP, ADP, AMP) and pyridine (NAD, NADH) nucleotides in human platelets have been measured by a simple and reproducible method. A rapid alkaline extraction allows a complete recovery of the compounds concerned. The metabolic ATP and ADP in the cytosolic fraction, the amount released upon thrombin stimulation, and the ADP bound to F-actin have also been evaluated. Analysis was performed by reverse-phase, isocratic high-performance liquid chromatography on a 5-microns Lichrosorb RP-18 column with uv detection at 254 nm.

Synthesis and antiplatelet activity of 2-(diethylamino)-7-ethoxychromone and related compounds

Abstract 2-(Diethylamino)-7-ethoxychromone 3a and its 2-(1-piperidinyl)analogue 3b were synthesized by reaction of 3-ethoxyphenol 1 with 3-(dialkylamino)-3-oxo-propanoic acid ethyl ester 2 in the presence of phosphorus oxychloride. With a view to improve their biological activity the above 7-ethoxychromones 3 were submitted to some structural modifications firstly involving the 4-CO group. The 4H-chromenes 4 and the 4-thiochromones 5 were obtained by action of suitable reagents. The compounds 5 were then easily transformed to 4-(methylthio)chromenylium iodides 6 . Then from the 2-(diethylamino)-7-ethoxychromone 3a were obtained with suitable reactions the 3,6-diamino derivative 8 , the 3- and 6-formyl derivatives 9a,b and the Mannich base 10 . By action of acetic anhydride this latter compound yielded the methylenebis derivative 11 . Most of the above compounds were tested in vitro for their inhibitory activities against human platelet aggregation induced by collagen, ADP and arachidonic acid. Among the tested compounds the 2-(diethylamino)-7-ethoxychromone 3a showed the highest activity.

Antiplatelet effect of 2-(diethylamino)-7-hydroxychromone

In this study the in vitro influence of 2-(diethylamino)-7-hydroxychromone (RC39II) on platelet aggregating responses, thromboxane A2 (TxA2) production, release reaction and intraplatelet cyclic AMP (cAMP) content has been investigated. The drug exerts a dose-dependent inhibitory effect on aggregating response to arachidonic acid, U46619, thrombin, collagen and calcium ionophore A23187. Inhibiting concentrations of RC39II also prevent platelet release reaction and TxA2 formation. RC39II potentiates platelet cAMP accumulation by Iloprost. Several studies, carried out on soluble cAMP phosphodiesterase (PDE) have shown that the drug inhibits phosphodiesterase in a dose-dependent manner. No effect was shown on adenylate cyclase activity from platelet membranes.