Time course of adaptation to low and high NaCl diets in the domestic fowl

Abstract

Short circuit currents (I _sc), resting electrical potential differences (p.d.) and resistances were measured in vitro for stripped rectal (“colonic”) and coprodeal epithelia from fowls transferred to low from high NaCl diet for 1, 2, 4 or 8 days (NaCl depletion), and from birds adapted to low NaCl diet and sacrificed 8, 16 and 24 h after NaCl-loading (resalination). NaCl-depletion enhancedI _sc and p.d. fully by 4 days in rectum but took 8 days in coprodeum (half times 1.2 days and 4 days respectively); rectal amino acid-sensitiveI _sc was abolished and amiloride-sensitiveI _sc was established by 4 days (half-time 1 day). Resistance changes were transient and relatively small in rectum, but coprodeal resistance decreased. Resalination reversed these changes very rapidly in both tissues (within 25–50 h; half times 10–20 h). It is concluded that responses to NaCl-depletion are mediated by aldosterone (and possibly by some other unknown agonist); responses to resalination may be due in part to suppressed aldosterone secretion and possibly to the evocation of some other controller (perhaps prolactin or corticosterone) antagonising aldosterone.