This study examined
circadian variation in
coagulation and
fibrinolytic parameters among Jcl:
ICR, C3H/HeN, BALB/cA, and C57BL/6J strains of
mice. Plasma
plasminogen activator inhibitor 1 (
PAI-1) levels fluctuated in a
circadian manner and peaked in accordance with the
mRNA levels at the start of the active phase in all strains.
Fibrinogen mRNA levels peaked at the start of rest periods in all strains, although plasma
fibrinogen levels remained constant. Strain differences in plasma
antithrombin (AT) activity and
protein C (PC) levels were then identified. Plasma AT activity was
circadian rhythmic only in Jcl:
ICR, but not in other strains, although the
mRNA levels remained constant in all strains. Levels of plasma PC and its
mRNA fluctuated in a
circadian manner only in Jcl:
ICR mice, whereas those of plasma
prothrombin,
factor X,
factor VII,
prothrombin time (PT), and activated partial
thrombin time (
APTT) remained constant in all strains. These results suggest that
genetic heterogeneity underlies
phenotypic variations in the
circadian rhythmicity of
blood coagulation and
fibrinolysis. The
circadian onset of thrombotic events might be due in part to the rhythmic
gene expression of
coagulation and
fibrinolytic factors. The present study provides fundamental information about
mouse strains that will help to understand the
circadian variation in
blood coagulation and
fibrinolysis.
