Changes in cytosolic calcium concentrations and cell morphology in single platelets adhered to fibrinogen-coated surface under flow.
Changes in intracellular calcium concentration [Ca2+]i of fura-2-loaded human platelet during its adhesion to a fibrinogen-coated surface were studied, using a flow chamber mounted on an epifluorescence microscope equipped with digital-ratio imaging. Adherent platelets were individually mapped under a scanning electron microscope to establish the possible correlation between adhesion-associated shape alterations and [Ca2+]i changes. We found that 1) there was no immediate [Ca2+]i elevation on platelet adhesion; 2) [Ca2+]i changes varied drastically platelets with a lag time ranging 10 to 200 s, averaging about 1 minute; 3) the pattern of [Ca2+]i changes varied drastically among individual adherent platelets; 4) the degree of [Ca2+]i elevation appeared to correlate with the extent of morphology change, with the vast majority ( > 90%) of spread platelets showed detectable [Ca2+]i changes; 5) neither morphological nor [Ca2+]i changes correlated with the lag time; 6) platelets treated with dimethyl-BAPTA (15 mumol/L) underwent normal shape change without [Ca2+]i elevation; 7) cytochalasin D (10 mumol/L) inhibited both shape change and [Ca2+]i elevation; 8) colchicine (1 mmol/L) was ineffective in both regards. We conclude that although platelet adhesion-associated shape changes may be accompanied with heterogeneous [Ca2+]i changes that are microfilament-dependent, [Ca2+]i changes do not happen immediately after platelet-surface contact and they are not required for adherent platelets to undergo postcontact morphological changes.
Jen
C J
CJ
Department of Physiology, National Cheng-Kung University Medical College, Tainan, Taipei, Republic of China.
Chen
H I
HI
Lai
K C
KC
Usami
S
S
D001792:Blood Platelets / Q000166:cytology / Q000502:physiology*; D002118:Calcium / Q000502:physiology*; D002448:Cell Adhesion; D048429:Cell Size; D005340:Fibrinogen / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans
D005456:Fluorescent Dyes; D005340:Fibrinogen; D002118:Calcium; D016257:Fura-2