Untersuchungen �ber den Einflu� von Papaverin auf Reaktionen der Blutpl�ttchen

“…In human platelets an increase in intracellular levels of cAMP is associated with the inhibition of platelet responses such as shape change, aggregation, adhesion, and release of granule contents [for reviews, see Salzman & Weisenberger (1972), Haslam (1973), and Mills (1982)] and thus may regulate platelet participation in physiological hemostasis and pathological thrombosis. Phosphodiesterase inhibitors such as the methylxanthines, papaverine, and dipyridamole have been shown to inhibit platelet activation (Ardlie et al, 1967;Markwardt et al, 1967;Vigdahl et al, 1971). Furthermore, such inhibitors potentiate the inhibition of platelets by such adenylate cyclase agonists as PGE,, PGI2, and adenosine (Markwardt et al, 1967;Mills et al, 1970; Mills & Smith, 1971;Jorgensen et al, 1979).…”

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confidence: 99%

Purification and characterization of a human platelet cyclic nucleotide phosphodiesterase

Grant¹,

Colman²

1984

Biochemistry

118

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A cyclic nucleotide phosphodiesterase was extensively purified from the 100000g supernatant fraction of human platelets. The purification was 2500-3000-fold with 30% recovery of activity. The enzyme was isolated by DEAE-cellulose chromatography followed by adsorption to blue dextran-Sepharose and elution with cAMP. The protein has a molecular weight of 140 000 as determined by gel filtration. On NaDodSO4-containing polyacrylamide gels the major band is at 61 000 daltons, suggesting that the enzyme may exist as a dimer in solution under nondenaturing conditions. The enzyme requires Mg2+ or Mn2+ for activity. The calcium binding protein calmodulin does not stimulate hydrolysis of cAMP by this enzyme. The purified enzyme hydrolyzes both cAMP and cGMP with normal Michaelis-Menten kinetics with Km values of 0.18 microM and 0.02 microM, respectively. The hydrolysis of cGMP, however, is only one-tenth as rapid as the hydrolysis of cAMP. Cyclic GMP does not stimulate cAMP hydrolysis but instead is a potent competitive inhibitor of cAMP hydrolysis. The enzyme is also competitively inhibited by the phosphodiesterase inhibitors papaverine, 3-isobutyl-l-methylxanthine, and dipyridamole. The enzyme did not cross-react with an antibody raised to a cAMP phosphodiesterase isolated from dog kidney, indicating that the enzymes are not immunologically related. The inhibition of cAMP hydrolysis by cGMP suggests a possible regulatory link between these two cyclic nucleotides. One of the roles of cGMP in platelets may be to potentiate increases in intracellular cAMP by inhibiting the hydrolysis of cAMP by this enzyme.

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“…The drugs dipyridamole and papaverine, which block the incorporation of adenosine into platelets (Markwardt, Barthel, Glusa & Hoffman, 1967;Born & Mills, 1969;Mills et al 1970) potentiate the inhibition of aggregation that adenosine causes. Adenosine and adenine nucleotides cause increases in 3': 5'-cyclic AMP in guinea-pig brain (Sattin & Rall, 1970) though subcellular preparations of adenylate cyclase from rat liver are inhibited by adenosine and by nucleotides (Moriwaki & Foa, 1970).…”

mentioning

confidence: 99%

The influence on platelet aggregation of drugs that affect the accumulation of adenosine 3′:5′-cyclic monophosphate in platelets

Mills

Smith

1971

Biochemical Journal

419

110

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1. The involvement of intracellular 3':5'-cyclic AMP in the inhibition of platelet aggregation by prostaglandin E(1), isoprenaline and adenosine has been examined by a radiochemical technique. Platelet-rich plasma was incubated with radioactive adenine to incorporate (14)C radioactivity into platelet nucleotides. Pairs of identically treated samples were taken, one for the photometric measurement of platelet aggregation induced by ADP, the other for estimation of the radioactivity of 3':5'-cyclic AMP. 2. Theophylline, papaverine, dipyridamole and 2,6-bis-(diethanolamino)-4-piperidinopyrimido[5,4d]pyrimidine (compound RA233) were found to inhibit 3':5'-cyclic AMP phosphodiesterase from platelets. At concentrations of 3':5'-cyclic AMP greater than 50mum the most active inhibitor was dipyridamole; at 3':5'-cyclic AMP concentrations less than 19mum, papaverine and compound RA233 were more active than dipyridamole. 3. In the presence of compound RA233 (50mum), the effectiveness of prostaglandin E(1) as an inhibitor of platelet aggregation was increased tenfold. Compound RA233 also increased the stimulation by prostaglandin E(1) of the incorporation of radioactivity into 3':5'-cyclic AMP. 4. Compound RA233 (50mum) increased the effectiveness of both adenosine and 2-chloroadenosine as inhibitors of aggregation by 70-100-fold, and in the presence of compound RA233 both adenosine and 2-chloroadenosine stimulated the incorporation of radioactivity into 3':5'-cyclic AMP; the extent of the stimulation was proportional to the logarithm of the nucleoside concentration. 5. Compound RA233 (100-500mum) inhibited platelet aggregation by itself and caused small increases in the radioactivity of 3':5'-cyclic AMP. Partial positive correlations were found between the radioactivity of 3':5'-cyclic AMP in platelets measured at the time of addition of the aggregating agent (ADP) and the extent to which the aggregation was inhibited. 6. The results are interpreted as indicating that adenosine, 2-chloroadenosine, isoprenaline, prostaglandin E(1) and drugs that inhibit platelet 3':5'-cyclic AMP phosphodiesterase all inhibit aggregation by a common mechanism involving intracellular 3':5'-cyclic AMP.

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Untersuchungen �ber den Einflu� von Papaverin auf Reaktionen der Blutpl�ttchen

Cited by 20 publications

References 23 publications

The Blood Platelet Release Reaction

The Blood Platelet Release Reaction

Purification and characterization of a human platelet cyclic nucleotide phosphodiesterase

The influence on platelet aggregation of drugs that affect the accumulation of adenosine 3′:5′-cyclic monophosphate in platelets

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