Sinus Node Pacemaker Cells Research Articles

Effects of 2-Deoxy-D-Glucose on the Contraction Frequency of the Isolated Atria from Fed and Fasted Rats

The mere exogenous substrate removal did not change the contraction frequency of the isolated rat atria. However, addition of 2-deoxy-D-glucose together with the glucose removal, elicited a decrease in the atrial frequency. This decrease was significantly greater in the atria from fed rats with respect to those from fasted rats. Near the end of the experiments, only in the atria from fed rats, transient irregular beating appeared. The results suggest that triglycerides constitute the major endogenous substrate of the sinus node pacemaker cells when rats have been previously fasted and that these cells have metabolic features similar to those of contractile fibres.

Spontaneous action potentials of cells in the canine sinus node.

Right atria were excised from the hearts of 20 young dogs (15 +/- 5 weeks old) and maintained in vitro in order to perform microelectrode impalements. The atria contracted spontaneously for at least 6 hours at a stable rate of 127/min when they were perfused with Krebs-Ringer bicarbonate solution through the sinus node artery. Cells within a small area near the sinus node artery and between the superior vena cava and right atrium consistently yielded transmembrane potentials typical of pacemaker cells. This area was verified histologically to be the midportion of the sinus node. Electrical characteristics of these sinus node pacemaker cells were: maximum diastolic potential, -56 +/- 7 mV (mean +/- 1 SD); action potential amplitude, 56 +/- 8 mV; overshoot, 0 +/- 2 mV. Smooth transitions from phase 4 to phase 0 were always present. From these experiments we conclude that the excised perfused canine right atrium provides a useful new experimental cardiac preparation because it maintains stable spontaneous activity for many hours in vitro and the sinus node within it is readily accessible for study by intracellular microelectrodes.