The Uptake and Metabolism of Adenosine in Human Blood Platelets

1975 ◽  
Author(s):  
J. P. M. Lips ◽  
J. J. Sixma ◽  
A. M. C. Trieschnigg ◽  
H. Holmsen
Keyword(s):  
Human Blood ◽  
Adenine Nucleotides ◽  
Blood Platelets ◽  
Uptake Mechanism ◽  
Low Concentrations ◽  
Adenosine Transport ◽  
Energy Dependent ◽  
Unchanged Form ◽  
Uptake And Metabolism ◽  
Human Blood Platelets

Adenosine is taken up tino intact washed human blood platelets by two independent carrier-mediated processes. The ‘low Km system’ has a Km of 9 uM, a V of 792 pMol/min/109, is energy dependent and has a Q10 of 1.71. This system is competitively inhibited by papaverine and dipyridamol. The high Km system has a Km of 9.4 mM, as V of 106 nMol/min/109 is also energy dependent and has a Q10 of 1.31. This system is competitively inhibited by adenine, that has a very high affinity (K1 = 5,8 uM).Evidence is presented that the low Km system transports adenosine in such a way, that it is directly incorporated into nucleotides. Adenosine transported by way of the high Km system arrives unchanged inside the platelets. At low concentrations all this adenosine is deaminated. At higher concentrations (5 mM) part of it is converted into adenine nucleotides and part of it is present in an unchanged form. Only a relatively small part is deaminated at high adenosine concentrations.The high Km system is inhibited by purines. The low Km system is only inhibited by purine ribosides. The presence of a double uptake mechanism and metabolic pathway has direct bearing on experiments that have been effected about the relation between adenosine transport and inhibition of ADP aggregation.

scholarly journals Short communication: possible association of newly absorbed serotonin with nonmetabolic, granule-located adenine nucleotides in human blood platelets

Blood ◽  
1975 ◽  
Vol 45 (3) ◽  
pp. 413-416
Author(s):  
H Holmsen ◽  
CA Setkowsky ◽  
HJ Day
Keyword(s):  
Guinea Pig ◽  
Human Blood ◽  
Short Communication ◽  
Adenine Nucleotides ◽  
Blood Platelets ◽  
Human Platelets ◽  
Serotonin Release ◽  
Release Reaction ◽  
Human Blood Platelets

[3H]-adenine-labeled human platelets in plasma were incubated with or without nonradioactive serotonin. Release reaction was then induced by ADP, epinephrine, collagen, or thrombin. Platelets that had been incubated with serotonin released four times as much serotonin as platelets incubated without serotonin. The specific radioactivities of the ATP and ADP released to plasma during release reaction induced with all four inducers were the same in both systems. This shows that when serotonin is taken up by human platelets, it enters the compartment containing nonmetabolic, granula-stored ATP, and not the compartment with metabolic extragranular ATP. These results suggest that the mechanism of serotonin storage in human platelets is similar to that in other species investigated, i.e., rabbit, guinea pig, and pig.

Synergism Between Adrenaline and Adenine Nucleotides in Producing Platelet Aggregation Responses

1979 ◽  
Author(s):  
B. Oppenheim ◽  
M.B.H. Youdim
Keyword(s):  
Platelet Aggregation ◽  
Synergistic Effect ◽  
Human Blood ◽  
Adenine Nucleotides ◽  
Blood Platelets ◽  
Second Phase ◽  
Structural Analogue ◽  
Aggregation Response ◽  
Human Blood Platelets

Recently we have shown that 5′-adenylylimidodiphosphate (AIP), a structural analogue of ATP, causes a transient aggregation of human blood platelets similar to that produced by 5-hydroxytryptamine (5-HT) (Brit. J. Pharmacol. 1979, in press). In addition AIP strongly inhibits the second phase of aggregation induced by adrenaline (A), noradrenaline, ADP and irreversible 5-HT when such a response is obtained. However, it does not affect collagen response, indicating that AIP is an inhibitor of release I (i.e. release is reversible. Like 5-HT, the aggregation to AIP can be enhanced by pretreatment (30-60 sec.) with low (0.1-0.5 μM) non-aggregating concentrations of A, but without exhibiting a second phase of aggregation. The synergistic effect of A (but not isoproterenol, 10-100 μM) was also observed with ATP and ADP. ATP by itself does not produce an aggregation response but it causes a 5-HT like response after preincubation with A. The potentiating effects of A on aggregation responses are selectively prevented by phentolamine (10 μM) but not by proparanolol (10 μM). The results suggest an α-adrenergic mediated effect.

Incorporation of Labelled Nucleotides and Aggregation of Human Blood Platelets

1966 ◽  
Vol 15 (01/02) ◽  
pp. 052-068 ◽  
Author(s):  
E. W Salzman ◽  
D. A Chambers ◽  
Lena L. Neri
Keyword(s):  
Platelet Aggregation ◽  
Methyl Ester ◽  
Human Blood ◽  
Platelet Rich Plasma ◽  
Adenine Nucleotides ◽  
Blood Platelets ◽  
Temperature Dependent ◽  
Sequence Of Events ◽  
Plasma Factor ◽  
Human Blood Platelets

SummaryAddition of ADP-8-C14 to platelet-rich plasma results in platelet radioactivity through a series of temperature-dependent reactions involving stepwise dephosphorylation of the nucleotide in plasma and then incorporation of the adenosine residue by the platelet, where it participates as a precursor in synthesis of platelet adenine nucleotides. This sequence of events, which requires a heat-labile nondialysable plasma factor, is blocked by 0.01 M KCN, by EDTA, by arginine methyl ester, by adenosine, and by AMP.ADP-induced platelet aggregation does not require the reactions outlined above and proceeds without ADP - breakdown and without binding of the ADP- molecule to the platelet. A possible mechanism of this phenomenon is suggested.

Short communication: possible association of newly absorbed serotonin with nonmetabolic, granule-located adenine nucleotides in human blood platelets

Blood ◽  
1975 ◽  
Vol 45 (3) ◽  
pp. 413-416 ◽  
Author(s):  
H Holmsen ◽  
CA Setkowsky ◽  
HJ Day
Keyword(s):  
Guinea Pig ◽  
Human Blood ◽  
Short Communication ◽  
Adenine Nucleotides ◽  
Blood Platelets ◽  
Human Platelets ◽  
Serotonin Release ◽  
Release Reaction ◽  
Human Blood Platelets

Abstract [3H]-adenine-labeled human platelets in plasma were incubated with or without nonradioactive serotonin. Release reaction was then induced by ADP, epinephrine, collagen, or thrombin. Platelets that had been incubated with serotonin released four times as much serotonin as platelets incubated without serotonin. The specific radioactivities of the ATP and ADP released to plasma during release reaction induced with all four inducers were the same in both systems. This shows that when serotonin is taken up by human platelets, it enters the compartment containing nonmetabolic, granula-stored ATP, and not the compartment with metabolic extragranular ATP. These results suggest that the mechanism of serotonin storage in human platelets is similar to that in other species investigated, i.e., rabbit, guinea pig, and pig.

Identification of 5-Hydroxytryptamine [5-HT] Storing Organelles in Isolated Megakaryocytes

1979 ◽  
Author(s):  
R. Seitz ◽  
W. Wesemann
Keyword(s):  
Electron Microscopy ◽  
Bone Marrow ◽  
Guinea Pig ◽  
Density Gradient ◽  
Human Blood ◽  
Blood Platelets ◽  
Uptake Mechanism ◽  
Dense Bodies ◽  
Percoll Density Gradient ◽  
Human Blood Platelets

Megakaryocytes were enriched from rat and guinea pig bone marrow by Percoll density gradient and/or Elutriator centrifugation, [3H]5-HT was incorporated into megakaryocytes by a time- and concentration dependent, saturable uptake mechanism comparable to 5-HT incorporation into human blood platelets. - Electron microscopy of megakaryocytes showed that the number of osmiophilic dense bodies is increased after incubation with 5-HT. These findings suggest that the osmiophilic dense organelles are the 5-HT storage sites within megakaryocytes and provide a mean to identify these organelles during their biogenesis.

Immune Reactions of Human Blood Platelets

1968 ◽  
Vol 20 (03/04) ◽  
pp. 327-335 ◽  
Author(s):  
Ch Mueller-Eckhardt ◽  
E. F Lüscher
Keyword(s):  
Human Blood ◽  
Immune Complexes ◽  
Room Temperature ◽  
Adenine Nucleotides ◽  
Blood Platelets ◽  
Human Platelets ◽  
Platelet Surface ◽  
Sh Group ◽  
Significant Release ◽  
Human Blood Platelets

SummaryThe effects of the SH-inhibitors monoiodoacetate (MIA) and N-ethylmaleimide (NEM) on washed human blood platelets and on reactions of the platelets with immune complexes and antiplatelet antisera were studied. The following results were obtained:1. In the concentration range from 0.01 to 1 mM, only MIA in the highest concentration had a direct effect on platelets, discernible by a small but significant release of adenine nucleotides.2. The reaction of human platelets with heterologous anti-platelet antisera, heat aggregated human gammaglobulin, and gammaglobulin-coated latex particles was inhibited by MIA in concentrations of 0.1 mM and by NEM in concentrations of 1 mM, and higher.3. The SH-inhibitors tested exerted their influence on the platelet and not on the immune agents.4. L-cysteine was unable to reverse the effect of the SH-inhibitors on platelets. If added at room temperature in equimolar amounts to MIA and NEM 10 min prior to their contact with platelets, it abolished the effect of NEM, but not of MIA.5. The inhibition by MIA and NEM of platelet reactions with a variety of immune agents is comparable to the impairment of thrombin-induced viscous metamorphosis by SH-blockers. The obtained results do not support the assumption that immune agents and thrombin react with different, SH-group-containing substrates on the platelet surface.

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