The Effects Of Premarin And Progesterone On The Activity And MRNA Expression Of TPA And PAI-1 In HUVEC

Objectives: To find out the effects of estrogen and progestin on the activity and mRNA expression of tissue-type plasminogen activator(tPA) and plasminogen activator inhibitor -1 (PAI-1) in human umbilical vein endothelial cells (HUVEC).Methods : HUVEC were cultured with premarin at various concentrations (0.025, 0.25, 2.5ng/ml) ,progesterone (Ing/ml) or premarin (2.5ng/ml) plus progesterone (Ing/ml) in medium, the activity of tPA and PAI-1 in the supernatant of HUVEC cultures was measured by chromogenic assays after 12 hours and 28 hours respectively. Reverse transciption- polymerase chain reation (RT-PCR) was used to analyze tPA and PAI-1 mRNA levels after 28 hours.Results : Exposure of HUVEC to premarin (0.25 > 2.5ng/ml) or premarin (2.5ng/ml) combined with progesterone (Ing/ml) for 28 hours significantly reduced the expression of tPA and PAI-1 mRNA, enhanced the activity of tPA, and decreased the activity of PAI-1.However, the effects were not observed with premarin (0.025ng/ml) or progesterone. There were no effects on activity of PAI-1 for 12 hours.Conclusions : 1 > Premarin can reduce the expression of tPA and PAI-1 mRNA of HUVEC, increase the activity of tPA and decrease theinactivity of PAI-1. Thus it enhances the fibrinolytic potential , which may play an important role of mechanism of cardiovascular protection of estrogen.2 ^ The lowest effective concentration of premarin may be at 0.25ng/ml ;Premarin (0.25ng/mK 2.5ng/ml) has significant effects on the activity of PAI-1 for 28 hours in HUVEC,while has no significant effects for 12 hours .The result indicates that the effects of premarin on PAI-1 in HUVEC are related to the dosage of premarin and the hours HUVEC exposed to it.3^ Progesterone probably has no direct effects on tPA and PAI-1 in HUVEC, but can dimilish the effects of estrogen partly .