ABSTRACT
Objective To determine whether nitric oxide may result in different effects on cardiac function at the different time points during the course of myocardial ischhemia and reperfusien of rats in viwo, and if so, to investigate the mechanisms involved.Methods Male adult rats were subjected to 30 minutes of myocardial ischemia followed by 5 hours of reperfusien. L-arginine was administrated at a bolus at both 10 minutes before and 50 minutes after reperfusion in early treatment group. The L-arginine was administrated at a bolus at both 3 and 4 hours after reperfusion in late treatment group. The following variables were measured: cardiac hemodynamic parameters, myocardial easpase 3 activity, iNOS and total NO content. Results Compared with vehicle group, administration of L-arginine at early reperfusion markedly reduced myocardial caspase 3 activity, and improved cardiac function. In strict contrast, administration of L-arginine at late reperfusion resulted in a significant increase in myocardial NOx content, myocardial apoptosis, and depressed the cadiac function. Conclusion Timely administration of L-arginine might inhibit apoptosis while late administration of L-arginine might enhance apoptosis.
ABSTRACT
Objective To observe the change of collagen in osteoarthritis and study the pathogenesis of osteoarthritis.Methods The right hind limb of twenty-four adult New Zealand White rabbits were immobilized with plaster cast in extension position for 10,20,30 and 40 days,respectively.Six animals without immobilization served as control.The articular cartilage of the medial femur condyle was harvested for transmission electron microscopy,in-situ hybridization of collagenⅡ,and immunohistochemistry of collagenⅠ,Ⅱ,Ⅲ.Results Transmission electron microscopy showed articular cartilage was destructed from the fine collagen fiber network of tangential zone.The fine collagen fiber network did not contain chondrocyte.Immunohistochemistry and in-situ hybridization showed that in earlier period of osteoarthritis,the collagen typeⅡand its gene expression firstly increased,then decreased with destruction of ultrastructure,and chondrocytes enhanced type Ⅱ collagen expressing and synthesizing mainly in transition zone and upper deep zone.In articular cartilage of osteoarthritis there was type Ⅲ collagen,instead of typeⅠcollagen.Conclusion In osteoarthritis,articular cartilage degenerated from tangential layer,in which collagen can not be repaired after destruction,this may contribute to the chondral degeneration.