Insulin, cortisol and catecholamines do not regulate circadian variations in fibrinolytic activity.
To evaluate possible hormonal regulators of the diurnal rhythm in fibrinolytic activity, we measured tissue plasminogen activator (t-PA) activity, plasminogen activator inhibitor activity (PAI-1), t-PA antigen, insulin, cortisol, and catecholamines in 6 healthy males (age 34 +/- 5) every 2 hours for 24 hours. Fibrinolysis was characterized by a peak in PAI-1 activity and a trough in t-PA activity at 0600 h. PAI-1 activity increased 92% and t-PA activity decreased 56% between 2400 h and 0600 h. t-PA antigen (principally a measure of t-PA/PAI-1 complex), peaked at 0800 h. In comparison, insulin levels were lowest at night when PAI-1 activity was rising. The weak inverse correlation between insulin and PAI-1 activity (r = -0.28, p less than 0.02), was not sufficient to explain the diurnal change in fibrinolysis. While cortisol demonstrated the expected circadian change, the increase in cortisol did not occur until 0400 h, 4-6 hours after the rise in PAI-1 and decrease in t-PA activity started. Supine resting plasma epinephrine and norepinephrine showed no circadian rhythm. From this data, we hypothesize that the increased level of PAI-1 in the morning consumes t-PA, leading to decreased t-PA activity and increased t-PA/PAI-1 complex. Further, we conclude that insulin, cortisol, and catecholamines are not responsible for the circadian rhythm of fibrinolysis.
Chandler
W L
WL
Department of Laboratory Medicine, University of Washington, Seattle 98195.
Mornin
D
D
Whitten
R O
RO
Angleton
P
P
Farin
F M
FM
Fritsche
T R
TR
Veith
R C
RC
Stratton
J R
JR
D000328:Adult; D002395:Catecholamines / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004837:Epinephrine / Q000097:blood; D005342:Fibrinolysis / Q000502:physiology*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000502:physiology*; D007328:Insulin / Q000097:blood / Q000502:physiology*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D015849:Plasminogen Inactivators / Q000378:metabolism; D010959:Tissue Plasminogen Activator / Q000378:metabolism
D002395:Catecholamines; D007328:Insulin; D015849:Plasminogen Inactivators; D010959:Tissue Plasminogen Activator; D006854:Hydrocortisone; D009638:Norepinephrine; D004837:Epinephrine