Cardiac dysfunctions such as myocardial functional failure and ventricular arrhythmia have been largely attributed to intracellular Ca2+ overload. One of the mechanisms of intracellular Ca2+ overload involves a rapid influx of Ca2+ via Na(+)-Ca2+ exchange during the reperfusion which utilizes the accumulation of Na+ in myocytes during ischemic cardiac arrest. Possible sources of the intracellular Na+ accumulation include Na+ channel, Na(+)-H+ exchange, Na(+)-Ca2+ exchange, and Na+ background current. In this study, we studied the role of the Na+ background current in intracellular Na+ accumulation during the cardiac arrest by measuring the Na+ background current in guinea pig ventricular myocytes with whole cell clamp method and evaluating the effects of cardioprotective drugs on the Na+ background current. The results were as follows: (1) The Na+ background inward current at -40 mV membrane potential was larger at Ca2+ free solution than 1.8 mM Ca2+ solution. (2) The Na+ background current was not affected by verapamil. (3) 2 microM O-(N, N-hexamethylene)-amiloride (HMA) decreased the Na+ background current at negative membrane potential. (4) The new cardioprotective drug, R 56865, decreased the Na+ background current. These results suggest that the Na+ background current plays a role in increasing the intracellular Na+ activity during high K+ cardioplegia and the blocking effect of myoprotective drugs, such as R 56865, on the Na+ background current may contribute to myocardial protection after cardioplegia.
Amiloride/pharmacology ; Animal ; Guinea Pigs ; Heart/*drug effects ; Heart Arrest, Induced ; Myocardium/metabolism ; Piperidines/pharmacology ; Potassium/pharmacology ; Sodium/*metabolism ; Support, Non-U.S. Gov't ; Thiazoles/pharmacology ; Verapamil/pharmacology

This study is to compare the effect of wound healing using three different types of chitin, which include the shapes of sponge, velvet, thick non-woven fabrics, and thin non-woven fabrics. The sponge type had more capacity to absorb the first discharge of a wound than the velvet type and the two non-woven fabrics types. Instead of absorbing the discharge effectively, the velvet type showed a difficulty to take off the dressing stuff from a wound since it was solidly stuck to the wound. The sponge type showed less infiltration of inflammatory cells, producing angiogenesis and fibroblast faster than any other types. Next, the thick non-woven fabrics type was a little more effective than the thin non-woven fabrics type: However, there was no difference between two types. The velvet type sustained the infiltration of inflammatory cells for the longest duration, producing slower angiogenesis and fibroblast. In wound contraction and wound healing, the sponge type was most effective with statistical significance than any other types(p<0.05). The two types of non-woven fabrics did not present any statistical significance in wound contraction, wound epithelization and wound healing(p>0.05). In conclusion, the sponge type showed the best effectiveness to absorb the early discharge, facilitating the progress of inflammatory phase to increase the healing rate. It induced an early healing of wound caused by wound contraction rather than by wound epithelization.
Bandages ; Chitin ; Chitosan* ; Fibroblasts ; Porifera ; Wound Healing* ; Wounds and Injuries*