Platelet Aggregation, Platelet Serotonin

Fuad Lechin, Bertha van der Dijs
Department of Physiological Sciences, Instituto de Medicina Experimental,
Universidad Central de Venezuela. Caracas, Venezuela
Dear Sir:
The article by Mimidis et al. [1] prompted us
to contribute some additional information.
The authors studied acute pancreatitis patients
showing increased platelet adhesiveness and
aggregation. They postulate that the platelet
activation factor is the most important
mediator involved in the process and triggers
platelet activation. They also discuss the
mechanisms played by the membrane integrin
glycoprotein IIb/IIIa. Furthermore, they made
reference to membrane receptors for
fibrinogen and the calcium-dependent linkage
formation between activated receptors and
bivalent fibrinogen which results in platelet
aggregation. They also referred to pro-
aggregatory mediators such as ADP, ATP,
platelet factor 4 (PF4), betathromboglobulin
(beta-TG), thromoboxane A2 (TXA2),
fibrinogen and thrombospondin which are
followed by the translocation of alpha-granule
membrane protein P-selectin (CD62). Finally,
they mentioned the role played by
phosphatidylserine which is the starting point
for the coagulation cascade. They also
referred to the alterations of the platelet
function described in models of systemic
inflammation such as ulcerative colitis,
Crohn's disease and acute pancreatitis.
With respect to all of the above, we would
like to further elucidate the role played by
platelet-serotonin (p-5HT) in thrombogenesis.
This factor, rather than the platelet count,
seems to constitute the true index of
thrombogenesis [2, 3]. With respect to the
above, we successfully treated five cases of
refractory idiopathic thrombocytopenic
purpura (ITP) using a neuropharmacological
therapy aimed at enhancing (central nervous
system) noradrenergic activity. Surprisingly,
restoration of p-5HT levels, rather than the
platelet count, was correlated with bleeding
stoppage and clinical improvement. The
above findings are consistent with the fact
that serotonin is stored in the delta granules of
The release of serotonin is considered to be
the "gold standard" assay for the detection of
thrombocyte activation [4]. The presence of
serotonin is covalently linked to fibrinogen
bound on the surface of the activated platelet
where it increases the retention of
procoagulant factors on the cell surface [5].
Serotonin, therefore, occupies a central role in
the hamostatic process, and its release is
considered the most reliable assay for platelet
activation [4].
Our findings are in line with those obtained
by Dominguez et al. [6] who showed a lack of
correlation between the platelet count and
bleeding in an experimental model of immune
thrombocytopenic purpura in mice. The fact
that not only acute pancreatitis [7, 8] but other
inflammatory diseases, such as ulcerative
colitis [9, 10] and Crohn's disease [11, 12,
13], showed similar platelet disorders is
consistent with findings which show that
these diseases present with increased platelet
aggregability secondary to the elevated
circulating adrenaline which is always
present. The latter phenomenon is responsible

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JOP. J Pancreas (Online) 2004; 5(4):237-239.
JOP. Journal of the Pancreas – – Vol. 5, No. 4 – July 2004. [ISSN 1590-8577]
both for the reduction of p-5HT and the
increase of plasma serotonin (f-5HT). Thus,
we believe that the fundamental role played
by platelet serotonin in thrombogenesis
should not have been omitted in the
discussion of the article by Mimidis et al. [1].
Received May 26th, 2004
Serotonin; Thrombosis
serotonin; ITP: idiopathic thrombocytopenic
purpura; PF4: platelet factor 4; p-5HT:
Fuad Lechin
Apartado 80.983
Caracas 1080-A
Phone: +58.212.961.1048
Fax: +58.212.961.0172
E-mail address:
1. Mimidis K, Papadopoulos V, Kartasis Z, Baka M,
Tsatlidis V, Bourikas G, Kartalis G. Assessment of
platelet adhesiveness and aggregation in mild acute
pancreatitis using the PFA-100TM system. JOP. J
Pancreas (Online) 2004; 5:132-7. [PMID 15138334]
2. Lechin F, van der Dijs B, Orozco B, Jahn E,
Rodriguez S, Scarlet B. Neuropharmacological
treatment of refractory idiopathic thrombocytopenic
purpura: roles of circulating catecholamines and
serotonin. Thromb Haemost June 2004 (In Press).
3. Lechin F, van der Dijs B. Platelet serotonin and
thrombostasis. J Clin Invest (Online), Letters, April 21,
4. Gobbi G, Mirandola P, Tazzari PL, Ricci F, Caimi
L, Cacchioli A, et al. Flow cytometry detection of
serotonin content and release in resting and activated
platelets. Br J Haematol 2003; 121:892-6. [PMID
5. Dale GL, Friese P, Batar P, Hamilton SF, Reed
GL, Jackson KW, et al. Stimulated platelets use
serotonin to enhance their retention of procoagulant
proteins on the cell surface. Nature 2002; 415:175-9.
[PMID 11805836]
6. Dominguez V, Govezensky T, Gevorkian G,
Larralde C. Low platelet counts do not cause bleeding
in an experimental
model of immune
thrombocytopenic purpura in mice. Haematologica
2003; 88:679-87. [PMID 12801844]
7. Lechin F, van der Dijs B, Lechin ME.
Neuropharmacological factors, biliary motility and
pancreatitis. JOP. J Pancreas (Online) 2002; 3:152-4.
[PMID 12221330]
8. Lechin F, van der Dijs B, Lechin M, Jara H,
Lechin A, Cabrera A, et al. Dramatic improvement
with clonidine of acute pancreatitis showing raised
catecholamines and cortisol plasma levels: report of
five patients. J Med 1992; 23:339-51. [PMID 1469335]
9. Lechin F, van der Dijs B, Insausti CL, Gómez F.
Treatment of ulcerative colitis with thioproperazine. J
Clin Gastroenterol 1982; 4:445-9. [PMID 6129273]
10. Lechin F, van der Dijs B, Insausti CL, Gómez F,
Villa S, Lechin AE, et al. Treatment of ulcerative
colitis with clonidine. J Clin Pharmacol 1985; 25:219-
26. [PMID 2860133]
11. Lechin F, van der Dijs B, Lechin S, Vitelli G,
Lechin ME, Cabrera A. Neurochemical, hormonal and
immunological views of stress: clinical and therapeutic
implications in Crohn's disease and cancer. In: Velazco
M, ed. Recent Advances in Pharmacology and
Therapeutics. International Congress Series, Vol 839.
Amsterdam, The Netherlands: Excerpta Medica, 1989:
12. Lechin F, van der Dijs B, Lechin ME. Illustrations
of some therapeutic results: neuropharmacological
therapy of Th-1 autoimmune diseases. In: Lechin F,
van der Dijs B, Lechin ME, eds. Neurocircuitry and
Neuroautonomic Disorders. Reviews and Therapeutic
Strategies. Basel, Switzerland: Karger, 2002:82-94.
13. Lechin F, van der Dijs B, Jackubowicz D, Camero
RE, Lechin S, Villa S, et al. Role of stress in the
exacerbation of chronic illness: effects of clonidine
administration on blood pressure and plasma
norepinephrine, cortisol, growth hormone and prolactin
concentrations. Psychoneuroendocrinology 1987;
12:117-29. [PMID 3602260]
Dear Sir:
In response to the letter of Drs. Lechin and
van der Dijs [1], we would like to express our

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JOP. J Pancreas (Online) 2004; 5(4):237-239.
JOP. Journal of the Pancreas – – Vol. 5, No. 4 – July 2004. [ISSN 1590-8577]
gratitude concerning the additional
information presented by the author. Indeed,
the crucial role of platelet-serotonin (p-5HT)
has been well-established in thrombogenesis
and the release of serotonin has been
proposed as the “gold standard” assay for the
detection of thrombocyte activation [2].
However, the purpose of our study was to test
a newly developed method of evaluating
primary hemostasis based on the platelet
function analyzer (PFA-100TM) in a
prethrombotic model such as acute
pancreatitis. This method had only been
applied to hemorrhagic diathesis and its
usefulness in thrombosis was unknown [3, 4,
5, 6]. Thus, we focused on testing the specific
method rather than commenting on the
underlying pathophysiology of platelets in
acute pancreatitis.
In conclusion, the authors’ statements
regarding the p-5HT levels and the potent use
of selective serotonin-reuptake inhibitors
(SSRIs) in acute pancreatitis serve as a
valuable proposal for future studies.
Konstantinos Mimidis
Vassilios Papadopoulos
Received June 1st, 2004
Keywords Platelet Adhesiveness; Platelet
Abbreviations p-5HT: platelet-serotonin;
SSRIs: selective serotonin-reuptake inhibitors
Konstantinos Mimidis
8, Chrisostomou Smirnis str.
1. Lechin F, van der Dijs B. Platelet aggregation,
platelet serotonin and pancreatitis. JOP. J Pancreas
(Online) 2004; 5(4):237-238.
2. Gobbi G, Mirandola P, Tazzari PL, Ricci F, Caimi
L, Cacchioli A, et al. Flow cytometry detection of
serotonin content and release in resting and activated
platelets. Br J Haematol 2003; 121:892-6. [PMID
3. Wuillemin WA, Gasser KM, Zeerleder SS,
Lämmle B. Evaluation of a Platelet Function Analyser
(PFA-100®) in patients with a bleeding tendency.
Swiss Med Wkly 2002; 132:443-8. [PMID 12457302]
4. Gosselin RC, Paglieroni T, Owings J, Utter G,
Jacoby R, Larkin EC. Decreased PFA-100 values is
associated with increased platelet activation. In: 7th
Annual Meeting of the European Hematology
Association. Florence, Italy, 6-9 June 2002. Bologna,
Italy: Monduzzi Editore, International Proceedings
Division, 2002. [ISBN. Book: 88-323-2606-X - CD-
ROM: 88-323-2607-9]
5. Mammen EF, Comp PC, Gosselin R, Greenberg C,
Hoots WK, Kessler CM, et al. PFA-100 system: a new
method for assessment of platelet dysfunction. Semin
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6. Escolar G, Cases A, Vinas M, Pino M, Calls J,
Cirera I, et al. Evaluation of acquired platelet
dysfunctions in uremic and cirrhotic patients using the
platelet function analyzer (PFA-100TM): influence of
hematocrit elevation. Haematologica 1999; 84:614-9.
[PMID 10406903]

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