AJP - Regulatory, Integrative and Comparative Physiology, Vol 261, Issue 6 1533-R1541, Copyright © 1991 by American Physiological Society
Aldosterone modulates electrogenic Cl secretion in the colon of the hen (Gallus domesticus)
W. Clauss, V. Dantzer and E. Skadhauge
Institut fur Veterinar-Physiologie, Freie Universitat Berlin, Federal Republic of Germany.
The regulation of Na and Cl transport in hen colon by mineralocorticoids
was investigated with isolated epithelia in vitro by histological and
electrophysiological techniques. The electrogenic transport of Na and Cl
was measured in Ussing chambers by the short-circuit current technique and
was identified by the specific inhibitors amiloride and bumetanide or by
the secretagogue theophylline. Hens were maintained either on low (LS)- or
on high-NaCl diets (HS), and the plasma aldosterone (PA) levels of these
groups were measured with radioimmunoassay. A group of HS hens received
injections of aldosterone at a 6-h schedule before experiments. A group of
LS hens was resalinated, and experiments were carried out at a 24-h
interval for up to 3 days after resalination. The LS diet stimulated PA
levels ninefold, compared with HS hens. Na transport was modulated by the
hormonal stimulus in a way that the apical Na entry switched from an
electrogenic Na-amino acid-hexose cotransport system completely to an
amiloride-sensitive Na channel. Electrogenic Cl secretion was induced by
theophylline and was inhibited by bumetanide. NaCl deprivation,
resalination or aldosterone injection modulated electrogenic Cl secretion
in parallel between 7 (HS) and 14.4 mu eq.cm-2.h-1 (LS), with pronounced
alteration in tissue conductance. These findings reveal a new action of
aldosterone that, besides stimulating Na absorption, also directly or
indirectly modulates Cl secretion.
