Temperature-dependence of LDL binding and activation of human platelets.
The effect of low density lipoprotein (LDL) on intracellular free calcium ion concentration ([Ca2+]i), taken as an index of the degree of platelet activation, was investigated in normal volunteers. At 37 degrees C LDL, in a dose of 20 micrograms of protein/ml, increased [Ca2+]i in all subjects tested (basal 57 +/- 11 to 113 +/- 19 nM). In contrast, when measurements were performed at 20 degrees C, no effect on [Ca2+]i was seen following LDL. Thrombin (0.2 U/ml) increased [Ca2+]i to 455 +/- 98 nM. When platelets had been exposed to LDL before thrombin stimulation, this increase was less pronounced (to 301 +/- 43 nM). Our finding of a temperature dependence of LDL induced increase in platelet [Ca2+]i supports the concept of a platelet-LDL receptor mediated mechanism. Furthermore, the lower thrombin response following LDL exposure suggests a LDL-thrombin interaction, possibly at the thrombin receptor level and/or calcium recruitment from the same stores.
Katzman
P L
PL
Department of Medicine, University of Manitoba, Winnipeg, Canada.
Bose
R
R
Walker
S
S
Perry
Y
Y
Bolli
P
P
D000328:Adult; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000097:blood; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008875:Middle Aged; D015539:Platelet Activation; D013696:Temperature; D013917:Thrombin / Q000378:metabolism
D008077:Lipoproteins, LDL; D013917:Thrombin; D002118:Calcium