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.

Preliminary studies on transmural potential and intensity of the short-circuit current in intestine of Gobius maderensis

The electrical difference (PD) and short-circuit current (Isc) across anterior intestine have been studied in vitro with solutions of different ionic composition in Gobius maderensis. 30 minutes after the beginning of the experiment a PD of about 2 mv negative serosa and an Isc of approximately 200 micro A/cm2 were recorded. Omission of sodium (Tris as substitute) from the luminal side or from both sides leads to an increment of 800% in PD more negative serosa together with an increase of 969% in Isc. In the absence of chloride (sulphate as substitute) the PD and Isc decreased and attained constant positive values. When the potassium was omitted from the luminal side or from both sides neither the P nor the Isc changed. These findings corroborate the assumption that active transport of chloride ions from mucosa to serosa is the major factor for transmural PD and account for the short-circuit current in the anterior intestine of Gobius maderensis.

[Oxygen uptake and active transport of glucose by small intestine of lizard Lacerta galloti (author's transl)]

The lizard intestine capability for active transport of D-glucose has been studied in vitro at 30 degrees C. A release of glucose and fructose from intestinal tissue to the medium took place throughout the incubation period. An active transport of glucose against a concentration gradient from the mucosal to the serosal compartment was found, but in a Na+--free medium (Tris as a substitute) this process was strongly inhibited--. The oxygen uptake was 50% higher in the presence of glucose than in its absence.