3,3',5'-Triiodothyronine inhibits collagen-induced human platelet aggregation.
To clarify further the activity of rT3, we examined the effect of rT3 on collagen-induced platelet activation as reflected by aggregation, serotonin release, and protein phosphorylation. rT3, T4, T3, and triiodothyroacetic acid inhibited collagen-induced platelet aggregation and serotonin release from platelets in a dose-dependent manner. However, thyronine did not inhibit collagen-induced platelet aggregation. The concentration at which rT3 inhibited by 50% collagen-induced platelet aggregation was 30 +/- 4 (mean +/- SE) mumol/L. rT3, T4, and T3 did not differ significantly in their abilities to inhibit platelet aggregation. Moreover, rT3 inhibited collagen-induced phosphorylation of the 20-kilodalton protein (myosin light chain) in platelets. In contrast, rT3 did not inhibit 12-O-tetradecanoylphorbol 13-acetate (TPA)- or thrombin-induced platelet aggregation and inhibited only minimally TPA-induced 40-kilodalton protein phosphorylation. These results suggest that rT3 inhibits collagen-induced platelet activation by inhibiting the activity of myosin light chain kinase and that it may be interesting to investigate some kinds of activity of rT3.
Masaki
H
H
Second Department of Internal Medicine, Kansai Medical University, Osaka, Japan.
Nishikawa
M
M
Urakami
M
M
Yoshimura
M
M
Toyoda
N
N
Mori
Y
Y
Yoshikawa
N
N
Inada
M
M
D001792:Blood Platelets / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D003094:Collagen / Q000494:pharmacology*; D006801:Humans; D010766:Phosphorylation; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011994:Recombinant Proteins; D012701:Serotonin / Q000097:blood; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin; D014284:Triiodothyronine / Q000494:pharmacology*; D014285:Triiodothyronine, Reverse / Q000494:pharmacology*
D001798:Blood Proteins; D010975:Platelet Aggregation Inhibitors; D011994:Recombinant Proteins; D014284:Triiodothyronine; D012701:Serotonin; D014285:Triiodothyronine, Reverse; D003094:Collagen; D013917:Thrombin; D013755:Tetradecanoylphorbol Acetate