Changes in phosphoinositide turnover, Ca2+ mobilization, and protein phosphorylation in platelets from NIDDM patients.
Enhanced platelet functions have been demonstrated in patients with non-insulin-dependent diabetes mellitus (NIDDM). This study evaluated abnormalities in platelet signal transduction in diabetic patients, including turnover of phosphoinositides, mobilization of intracellular Ca2+, and phosphorylation of 20,000- and 47,000-Mr proteins (P20 and P47). Washed platelets were obtained from 6 patients with NIDDM whose platelet aggregation rates were abnormally elevated (DM-A group), 11 NIDDM patients with normal platelet aggregation rates (DM-B group), and 8 age-matched healthy control subjects. The mass and specific radioactivity of phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol (PI), and phosphatidic acid (PA) in 32P-labeled platelets were not different among the three groups. Hydrolysis of PIP2, PIP, and PI; accumulation of PA; and phosphorylation of P20 in platelets stimulated by 0.05 U/ml thrombin were significantly increased in the DM-A group compared with the control or DM-B group. There was no difference in P47 phosphorylation among the three groups. On the contrary, P20 and P47 phosphorylation induced by 50 nM of 12-O-tetradecanoylphorbol-13-acetate, an activator of protein kinase C, was significantly decreased in the DM-A group. Additionally, the intracellular free Ca2+ concentration [( Ca2+]i) was measured with the fluorescent Ca2+ indicator fura 2. Although the basal [Ca2+]i value was similar in the three groups, the rise in [Ca2+]i induced by 0.05 U/ml thrombin in the presence and the absence of extracellular Ca2+ was significantly higher in the DM-A group than the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Ishii
H
H
Third Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Umeda
F
F
Hashimoto
T
T
Nawata
H
H
D000328:Adult; D001792:Blood Platelets / Q000378:metabolism* / Q000502:physiology; D001798:Blood Proteins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism / Q000502:physiology; D009218:Myosins / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D010750:Phosphoproteins; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001798:Blood Proteins; D010712:Phosphatidic Acids; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D010761:Phosphorus Radioisotopes; C039077:platelet protein P47; D011493:Protein Kinase C; D009219:Myosin-Light-Chain Kinase; D009218:Myosins; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium