AJP - Regulatory, Integrative and Comparative Physiology, Vol 239, Issue 3 285-R290, Copyright © 1980 by American Physiological Society
In vitro studies of sodium transport across the lower intestine of a desert parrot
E. Skadhauge and T. J. Dawson
The lower intestine (coprodeum and colon) of the Australian parrot, the
galah, was mounted in Ussing chambers. Short-circuit current (SCC),
electrical potential difference (PD), and unidirectional fluxes of Na and
Cl were measured in birds that were fed mixed seeds or were NaCl loaded.
The net Na transport of both coprodeum and colon was nearly equal to the
SCC, and the flux ratio for Cl was unity. In birds which received mixed
seeds, average coprodeal Na transport was 7.8 mu eq . cm-2 . h-1, and PD
was 19 mV. The Km for Na was 5.7 meq/l. In colon, Na transport was reduced
by 67% and PD by 70%. The ratio between unidirectional Na and Cl fluxes in
the serosa-mucosa direction was 0.7. Salt loading suppressed coprodeal, but
increased colonic Na transport. The coprodeal and colonic SCC and NA
transport of birds receiving mixed seeds were inhibited by amiloride on the
mucosal side. Colonic SCC of NaCl-loaded birds was only slightly reduced by
amiloride (by 17%), but stimulated by amino acids (by 18%).
