Comparative studies on the transmural potential difference and the intensity of the short-circuit current between the duodenum and the ileum of pigeon.

The transmural potential difference (PD), short circuit current intensity (Isc) and tissue resistance has been studied in duodenum and ileum of pigeon (Columbia livia var domestica) in media of different ionic compositions. When the tissue is incubated in a standard solution, the PD across the duodenum is approximately zero, while across the ileum is 7.2 mV (serosa positive with respect to mucosa). The PD and Isc measurements in duodenum in the absence of sodium on one hand and in the absence of chlorine on the other, reveal the existence of an active sodium absorption from mucosa to serosa, which draws chlorine along in the same direction. When sodium is substituted in the ileon (Tris as substitute), the PD and the Isc show a marked increase in serosa negativity. In the absence of the chloride ion sulphate as substitute) in ileon the PD and the Isc tend to zero, which indicate that the presence of the ion is necessary for the sodium transport.