Junctional resistance and action potential delay between embryonic heart cell aggregates.

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Abstract
Spheroidal aggregates of embryonic chick ventricle cells were brought into contact and allowed to synchronize their spontaneous beats. Action potentials were recorded with intracellular and extracellular electrodes. The degree of electrical interaction between the newly apposed aggregates was assessed by measuring the delay or latency (L) between the entrained action potentials, and by determining directly interaggregate coupling resistance (Rc) with injected current pulses. Aggregate size, contact area between the aggregates and extracellular K concentration .**GRAPHIC**. were important variables regulating the time-course of coupling. When these variables were controlled, L and Rc were linearly related after beat synchrony was achieved. In 4.8 mM .**GRAPHIC**. L/Rc = 3.7 ms/M.OMEGA.; in 1.3 mM .**GRAPHIC**. L/Rc = 10.1 ms/M.OMEGA.. Action potential delay between heart cell aggregates can be related quantitatively to Rc.