Avian colonic ion transport: effects of corticosterone and dexamethasone.
1. Corticosterone, a natural corticosteroid hormone in birds, when injected into domestic fowl (Gallus domesticus) (2000 micrograms.kg-1, 4-5 h before experiment) increases both the basal Isc (short-circuit current) and amiloride-sensitive Isc as well as the PD across the colon in vitro. Dexamethasone, a synthetic analogue (650 micrograms.kg-1, 4-5 h before experiment) also increases the basal and amiloride-sensitive Isc as well as PD in these preparations. 2. In marked contrast, longer term injection or infusion of dexamethasone (650 micrograms.kg-1) for 3 or more days caused a decline in basal Isc and PD (the PD often reversed with the serosal side becoming electronegative) and a drop in resistance. However in these preparations, the amiloride-sensitive Isc was significantly elevated which could be accounted for by an increase in net Na flux. 3. No significant change occurs in net flux of Cl or K although unidirectional fluxes in both directions were increased for both ions in birds given dexamethasone for 3 days. 4. A disparity between the basal Isc and the amiloride-sensitive Isc appeared in these preparations from dexamethasone injected birds reflecting the transport of other ions, possibly HCO3- or H+. The possible role of corticosterone in mineral metabolism of birds is discussed.
Grubb
B R
BR
Department of Anatomy, Physiological Sciences and Radiology, School of Veterinary Medicine, North Carolina State University, Raleigh 27606.
Bentley
P J
PJ
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002645:Chickens; D002712:Chlorides / Q000378:metabolism; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D003345:Corticosterone / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology*; D004594:Electrophysiology; D007477:Ions; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D002712:Chlorides; D007477:Ions; D000584:Amiloride; D003907:Dexamethasone; D012964:Sodium; D011188:Potassium; D003345:Corticosterone