Aldosterone effects on electrolyte transport of the lower intestine (coprodeum and colon) of the fowl (Gallus domesticus) in vitro

Hens were maintained on commercial (high-Na) poultry food or on a wheat and barley (WB; low-Na) diet. Stripped mucosae from coprodeum and colon were mounted in a Ussing chamber, and short-circuit current (I_sc), electrical potential difference (PD), and tissue resistance were measured. Tissue responses to addition of amino acids and amiloride were assessed. Coprodeum from commercial-diet birds had near-zero I_sc and PD. WB diet enhanced the average I_sc to 201 μA/cm² and the PD to 33 mV. The I_sc and PD were abolished by amiloride, but were not responsive to amino acids. Colon from commericial-diet birds had fairly high I_sc (134 μA/cm²) and PD (10 mV); I_sc and PD were increased by amino acids (by 45%) and not affected byamiloride. WB diet augmented I_sc to 379 μA/cm² and PD to 20 mV, abolished amino acid sensitivity, and induced almost complete sensitivity to amiloride. Birds maintained on WB diet had higher plasma aldosterone concentrations (9.6 pg/100 μl) than commercial-diet birds (5.8 pg/100 μl), but diet did not affect plasma corticosterone concentrations. In vivo injections of aldosterone (32–128 μg/kg body weight) into commercial-diet birds induced changes in I_sc and PD of coprodeum and colon, and changes in amino acid and amiloride sensitivity of colon, resembling the changes associated with WB maintenance, but of generally lesser magnitude. It is concluded that aldosterone injections reproduced qualitatively all the effects of a low-Na diet.