Na-transport during long-term incubation of the hen lower intestine: no aldosterone effect.

1. In order to test the aldosterone effect in vitro, Na-transport of the coprodeal epithelium from hens on low-NaCl diet was measured in the Ussing chamber for up to 8 hr. Short-circuit current (SCC, near equal to the amiloride inhibitable Na-transport) was recorded. 2. Incubation media were either Krebs-phosphate or bicarbonate buffer with and without addition of beta-hydroxybutyrate, glutamine and mannose as "metabolic fuels". The media were replaced every hour. The Krebs-phosphate buffer was further tested with and without indomethacin and media replacement. Na-transport was best maintained in this buffer with replacement: SCC at 4 hr: 156 +/- 21 microA/cm2, 8 hr: 73 +/- 14 microA/cm2. 3. The aldosterone experiments were carried out on tissues from hens resalinated for 24 hr. No effects were demonstrated at concentrations up to 10(-5) M. The SCC showed an unexpected raise within 2-4 hr to a very high level (4 hr: 221 +/- 61 microA/cm2) both in the control and in all aldosterone-treated tissues. This SCC decreased slowly to 210 +/- 29 microA/cm2 at 8 hr. It was abolished by amiloride. 4. No increase in SCC was observed in tissues from hens after 48 and 72 hr of resalination either after aldosterone or on chronic high-NaCl diet.