3 DIFFERENT GATING MODELS FOR INACTIVATION OF THE I-TO IN VENTRICULARMYOCYTES OF RATS AND MICE

Kinetic models to describe the time course of the Ca2+-independent out ward potassium current (I-to) in cardiac ventricular cells were constr ucted. The I-to traces were recorded from isolated myocyte's of rats a nd mice using the whole-cell configuration of the patch-clamp techniqu e. An iterative method was developed to eliminate the capacitive trans ient overlapping the early part of the I-to. The isolated I-to curves were then fitted by Hodgkin-HuxIey type functions and different inacti vation gating mechanisms were identified in various groups of the anim als. In some Wistar rats a single inactivation route was found. Anothe r group of Wistar rats and diabetic BB/Mol rats showed two independent inactivation pathways both of which resulted in a completely closed c hannel. In lean specimen of C-57 mice and in streptozotocin-treated Wi star rats the two inactivation gates gave closed channels only when bo th parallel inactivating transitions have been completed. In this case a possible interaction between the gating particles has been revealed .