[Measurement of cytoplasmic Ca2+ activity in myocardia with Ca(2+)-sensitive microelectrode]

The improved neutral ligand ETH1001 Ca(2+)-sensitive microelectrodes (Ca-ISE, tip diameter 0.4-0.8 mumol.L-1) are highly ion selective and sensitive and therefore can be reliably used to measure cytoplasmic Ca2+ activity (alpha iCa) in myocardia. The resting alpha iCa in guinea-pig ventricular trabecula, canine ventricular myocardia and Purkinje fibers were respectively 0.19 +/- 0.01, 0.20 +/- 0.02 and 0.46 +/- 0.07 mumol.L-1. Three mumol.L-1 strophantin G increased the resting and dynamic myocardial alpha iCa by 0.18 +/- 0.02 and 6.69 +/- 2.09 mumol.L-1 respectively, as well as engendered triggered activity (TA). When pretreated with 100 mumol.L-1 dauricine (Dau), strophantin G could no longer increase alpha iCa and TA disappeared. It is suggested thus the applicability of Ca-ISE for measurement of myocardia alpha iCa and TA is obvious.