| Pei-Yuan Chen, Tze-Che Wang, Shiaw-Wen Chien, An-dao Lo |
------>authors3_c=None ------>paper_class1=2 ------>Impact_Factor=None ------>paper_class3=0 ------>paper_class2=0 ------>vol= ------>confirm_bywho=hansun ------>insert_bywho=pychen ------>Jurnal_Rank=None ------>authors4_c=None ------>comm_author= ------>patent_EDate=None ------>authors5_c=None ------>publish_day=None ------>paper_class2Letter=None ------>page2= ------>medlineContent= ------>unit=E0100 ------>insert_date=20010323 ------>iam=1 ------>update_date= ------>author=??? ------>change_event=5 ------>ISSN=None ------>authors_c=None ------>score=305 ------>journal_name=??????????? ------>paper_name=Relationship Between the Activation of Na+/H+ Exchanger and Intracellular Ca2+ Concentration in Platelet ------>confirm_date=20020501 ------>tch_id=067011 ------>pmid=8383969 ------>page1= ------>fullAbstract=The aim of the present study was to evaluate the regulatory relationship between the cytosolic free calcium concentration ([Ca2+]i and cytosolic pH (pHi). [Ca2+]i and pHi were measured using the fluorescent dyes fura-2 and BCECF [2~,7~-bis-(carboxyethyl)-5,6-carboxyfluorescein] respectively. In a medium with 1 mmol/l extracellular calcium, thrombin (2.5 units/ml) induced an increment in [Ca2+]i of 638 +/- 31 nmol/l (n = 5) and an intracellular alkalinization of 0.14 +/- 0.01 pH units (n = 8). Both responses were dependent on the concentration of thrombin, displaying a sigmoidal dose-response pattern. The intracellular alkalinization was dependent upon extracellular Na+ and was amiloride-sensitive, indicating that it was mediated by activation of the Na+/H+ exchanger. When extracellular calcium was chelated with EGTA prior to the addition of thrombin, the intracellular alkalinization was not affected (0.15 +/- 0.02 at 2.5 units/ml thrombin, n = 8). Under these circumstances, the [Ca2+]i increment represents mobilization from internal stores, reaching 157 +/- 42 nmol/l at 2.5 units/ml thrombin. When platelets were preloaded with the intracellular calcium chelator MAPTAM (1,2-bis-5-methylaminophenoxylethane-NNN~-tetraacetoxymethyl acetate) to block the increase in [Ca2+]i induced by thrombin, no increment in pHi was observed. Moreover, MAPTAM-loaded calcium-depleted platelets had a basal pHi that was more acidic than in the presence of 1 mmol/l extracellular calcium (6.93 +/- 0.09 versus 7.14 +/- 0.01, n = 26, P < 0.001). Ionomycin induced an elevation of [Ca2+]i that was accompanied by a concomitant increase in pHi, which was Na(+)-dependent and amiloride-sensitive. [Ca2+]i and pHi increases induced by ionomycin were both dependent on the concentration of ionomycin. In conclusion, an increase in [Ca2+]i is necessary for the agonist-induced activation of the Na+/H+ exchanger in platelets. Non-agonist-induced increases in [Ca2+]i seems to prompt activation of the exchanger. In addition, Ca(2+)-depleted platelets have a more acidic basal pHi, indicating that the basal level of [Ca2+]i is also important for maintaining the basal pHi. ------>tmu_sno=None ------>sno=2893 ------>authors2=None ------>authors3=None ------>authors4=None ------>authors5=None ------>authors6=None ------>authors6_c=None ------>authors=Pei-Yuan Chen, Tze-Che Wang, Shiaw-Wen Chien, An-dao Lo ------>delete_flag=0 ------>SCI_JNo=None ------>authors2_c=None ------>publish_area=None ------>updateTitle=Intracellular calcium mobilization and activation of the Na+/H+ exchanger in platelets. ------>language=2 ------>check_flag= ------>submit_date= ------>country=None ------>no= ------>patent_SDate=None ------>update_bywho= ------>publish_year=1997 ------>submit_flag= ------>publish_month=None |