title: Function and regulation of the avian caecal bulb: influence of dietary NaCl and aldosterone on water and electrolyte fluxes in the hen (Gallus domesticus) perfused in vivo.
abstract: The function of the caecal bulb, and its adaptation to chronic high- or low-Na+ intake, was investigated by in vivo perfusion of anaesthetised birds. Effects of acute aldosterone injection (125 micrograms.kg-1 body mass) were also measured. Evidence was found for primary active net absorption of Na+, inducing parallel Na-linked absorption of water and Cl- and secretion of K+. Around 20-35% of total Cl- absorption and K+ secretion were independent of Na+ fluxes, and these components appear to be driven by passive processes with apparent conductances of 6.3 X 10(-3) (GCl) and 1.1 X 10(-3) (GK) S.cm-2. Acetate (40 mM) stimulated Na+ fluxes (8.5-9.9 microEq.cm-2.h-1) and Na-linked water fluxes (27-44 microliters.cm-2.h-1). Increased coupling ratios (2.9-4.6 microliters.microEq-1) and other data indicate that these effects may be due to increased osmotic permeabilities of barriers involved in the Na-linked water transfer pathway. Low-Na+ maintenance enhanced EPD (49-69 mV, serosa positive) and all net fluxes: JNa (6.8-11.6); JK (-3.2--4.3); JCl (4.3-5.6 microEq.cm serosal area-2.h-1); Jv (28-43 microliters.cm-2.h-1) (mucosal-serosal fluxes positive). Acute aldosterone enhanced JNa (10.8-14.0 microEq.cm-2.h-1) and EPD (54-66 mV) by 3 h after injection, but had no effect on the Na-linked components of JK or JCl.
authors.affiliation: School of Pure and Applied Biology, University of Wales, Cardiff, United Kingdom.
authors.forename: D H
authors.initials: DH
authors.lastname: Thomas
authors.forename: E
authors.initials: E
authors.lastname: Skadhauge
mesh_terms: D000450:Aldosterone / Q000494:pharmacology; D000818:Animals; D001834:Body Water / Q000378:metabolism* / Q000502:physiology; D002432:Cecum / Q000378:metabolism / Q000502:physiology*; D002645:Chickens / Q000378:metabolism / Q000502:physiology*; D004573:Electrolytes / Q000378:metabolism* / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D004573:Electrolytes; D012965:Sodium Chloride; D000450:Aldosterone