Endothelin (ET) is a potent and long - acting vasoconstrictor peptide consisiting of 21 amino acids, and recently isolated from a medium of cultured porcine endothelial cells. To study its tracer kinetics property, we injected 125I -labelled ET into rat veins. The results are shown that the half time of the distribution phase and that of the elimina-tion phase of 125I-ET in plasma are 5. 56 ?0. 04 min and 210. 13?38. 09 min, respectively. The125 - ET were widely distributed in various organs. The lung and kindney were the tissues with the highest grain density. Study of those in mouse blood and tissues showed similar results. KEY WORDS endothelin; tracer kinetics; dynamics; tissues; plasma

AIM　As one of the reactive oxygen species, toxic dose of H2O2 leads to the necrosis or apoptosis of many kinds of cells. It is nuclear whether these processes are related with the changes of nuclear Ca2+ elicited by H2O2. This study on the effect of taurine on changes of nuclear and cytosolic (Ca2+) elicited by H2O2 in rat vascular smooth muscle cells. METHODS　The techniques of Fluo-3 and laser scanning confocal microscopy were used. RESULTS　Rapid and sustaining rise of nuclear ［Ca2+］ (［Ca2+］n) and cytosolic ［Ca2+］(［Ca2+］c) were found in cultured rat vascular smooth muscle cells upon adding of 0.5% H2O2. Pretreatment of the cells with 20 mmol*L-1 taurine, a regulator of cellular Ca2+ homestasis, significantly decreased the rise amplitude of ［Ca2+］n (P<0.05), but failed to affect that of ［Ca2+］c (P>0.05) elicited by H2O2. It was suggested that the changes of ［Ca2+］n and ［Ca2+］c have different respond to taurine. CONCLUSION　It was concluded that there exist the independent regulating mechanisms of Ca2+ in the nucleus from differences between the nucleus and cytosol Ca2+ in sensitivity to action of H2O2 and taurine.

AIM As one of the reactive oxygen species, toxic dose of H 2O 2 leads to the necrosis or apoptosis of many kinds of cells. It is nuclear whether these processes are related with the changes of nuclear Ca 2+ elicited by H 2O 2. This study on the effect of taurine on changes of nuclear and cytosolic (Ca 2+ ) elicited by H 2O 2 in rat vascular smooth muscle cells. METHODS The techniques of Fluo 3 and laser scanning confocal microscopy were used. RESULTS Rapid and sustaining rise of nuclear [Ca 2+ ] ([Ca 2+ ] n) and cytosolic [Ca 2+ ]([Ca 2+ ] c) were found in cultured rat vascular smooth muscle cells upon adding of 0 5% H 2O 2. Pretreatment of the cells with 20 mmol?L -1 taurine, a regulator of cellular Ca 2+ homestasis, significantly decreased the rise amplitude of [Ca 2+ ] n ( P 0 05) elicited by H 2O 2. It was suggested that the changes of [Ca 2+ ] n and [Ca 2+ ] c have different respond to taurine. CONCLUSION It was concluded that there exist the independent regulating mechanisms of Ca 2+ in the nucleus from differences between the nucleus and cytosol Ca 2+ in sensitivity to action of H 2O 2 and taurine.