Diabetes Care, Vol 16, Issue 1 178-183, Copyright © 1993 by American Diabetes Association
Deranged platelet calcium homeostasis in poorly controlled IDDM patients
F Pellegatta, F Folli, P Ronchi, L Caspani, L Galli and AM Vicari
Department of Medicine, IRCCS H. San Raffaele, Milano, Italy.
OBJECTIVE--Platelet hyperfunction frequently occurs in IDDM. As in many
other cellular systems, cytosolic free Ca plays a key role in platelet
activation. RESEARCH DESIGN AND METHODS--We measured cytosolic free Ca
concentration ([Ca2+]i) by means of the fluorescent probe fura-2 in 60 IDDM
patients (mean age 30.8 yr, range 18-50 yr) and in 31 age-matched healthy
control subjects. Platelets were studied in both resting conditions and
after stimulation with thrombin at 0.05, 0.1, and 0.5 U/ml. RESULTS--No
differences were noted between control subjects and diabetic patients, as a
whole. Patients with a poor metabolic control (HbA1c > 8%) had
significantly (P < 0.01 and P < 0.03) higher [Ca2+]i in resting
platelets. The presence or absence of retinopathy did not modify resting
platelet [Ca2+]i. After stimulation with thrombin, a significantly (P <
0.009) higher rise of platelet [Ca2+]i was observed only in those patients
who were both free from complications and had good metabolic control. A
highly significant (P < 0.001) correlation was found between resting
[Ca2+]i and both blood cholesterol and HbA1c in the diabetic patients.
Platelets from 10 young healthy subjects also were studied after in vitro
incubation with various glucose concentrations (from 1.68 to 56 mM):
resting and thrombin-stimulated platelet [Ca2+]i and thrombin-induced
aggregation were not modified. CONCLUSIONS--These data confirm that
platelet hyperfunction is present in IDDM patients who have unsatisfactory
metabolic control, and give evidence that such an activation involves Ca
homeostasis. Acute variations of blood glucose concentration are probably
not influent, in this respect.