Effect of thyroxine on fibrinolytic system in rat.

Thyroid hormones have many effects on the cardiovascular system. Thyroid dysfunction accelerates atherosclerosis not only through conventional risk factors (dyslipidemia) but they also show a very close relationship with hemodynamic parameters. Thyroxine is determinant of the several components of fibrinolytic system even though the exact relationship is far from clear. Present study was carried out to determine the effect of thyroxine on fibrinolytic parameters such as plasminogen activators (PA) in rat heart, levels of PA and plasminogen activator inhibitor (PAI), glucose in plasma and serum lipid profile. Rats were injected with 50 ug eltroxine/100 gm–1 body weight intraperitoneally for one week. Compared with controls, thyroxine treatment increased PA activity significantly in rat heart. No changes were seen in PA, PAI and glucose in plasma of two groups of rats. A significant decrease in total cholesterol and LDL-cholesterol levels was seen in serum of treated group resulting in the decrease of LDL/HDL and Total cholesterol/HDL-cholesterol ratios. These results suggest that thyroxine treatment may have considerable clinical significance. It raised PA activity in heart as well as reduced cholesterol content in blood. It is possible that thyroxine treatment may confer a beneficial effect on cardiovascular risk.

Effect of thyroxine on plasminogen activator and inhibitor activity in rat.

Thyroid hormones influence mineral metabolism, distribution of water and electrolytes and are therefore of great importance in the maintenance of homeostasis under normal and diseased conditions such as renal failure. The present study was carried out to determine the effect of thyroxine on fibrinolytic parameters such as plasminogen activators (PA) in rat kidney, levels of PA and plasminogen activator inhibitor (PAI), glucose in plasma and serum lipid profile injected with thyroxine (75 microg eltroxine/ 100 g(-1) body weight, ip for 7 days). Treatment increased PA activity significantly in rat kidneys. No changes were seen in PA, PAI and glucose in plasma of rats. There was significant decrease in total cholesterol and LDL-cholesterol levels in serum of treated group resulting in the decrease of HDL/LDL and total cholesterol/cholesterol ratios. However, triglycerides and VLDL showed significant higher activity in the serum of treated group as compared to controls. The results suggest beneficial effects of thyroxine treatment by increasing PA activity in kidney and reducing the cholesterol content in blood. It may be helpful to prevent hypercoagulable state by maintaining the normal homeostatic balance and restoring renal function.

Effect of growth hormone on fibrinolytic system in rat.

Growth hormone deficiency (GHD) is associated as a risk factor in increased mortality from cardiovascular diseases. Abnormal lipid profile and increased levels of plasminogen activator inhibitor (PAI) and fibrinogen have been noted in GHD patients. Present study was carried out to investigate the effect of growth hormone (GH) on plasminogen activator (PA) activity in heart, levels of PA, PAI, glucose and fibrinogen in plasma and serum lipid profile. Rats were injected 125 mU GH kg-1 body weight subcutaneously daily for one week. PA activity was significantly higher in the heart of GH treated rats as compared to controls. GH treatment decreased plasma glucose and fibrinogen levels significantly. No significant differences were seen in PA, PAI in plasma, triglycerides and total cholesterol in serum of the two groups of rats. A significant increase in high density lipoprotein cholesterol (HDL) occurred in GH treated group resulting into a decrease in LDL/HDL ratio. The results indicate that GH may be beneficial in cardiovascular diseases as it decreases the levels of plasma fibrinogen and increases the level of HDL in blood and also increases the level of PA in heart.