Fasting alters basal and stimulated ion transport in piglet jejunum.
Three-week-old piglets were used to study the effects of short-term fasting on jejunal ion transport. A 48-h fast significantly reduced mucosal weight, villus height, and crypt depth. Fasting increased basal short-circuit current (Isc), which reflects active ion transport, and total tissue conductance (Gt) of muscle-stripped jejunal sheets mounted in Ussing chambers. Increases in Isc evoked by carbachol, serotonin, histamine, prostaglandin E2, or Escherichia coli heat-stable enterotoxin were significantly greater in the fasted piglets. Isc responses to mucosal D-glucose were also enhanced by the fast. Under basal conditions, unidirectional and net fluxes of Na+ and Cl-, as well as serosal-to-mucosal inulin fluxes, were significantly increased in fasted piglets. In fed piglets, carbachol increased net Cl- secretion by stimulating serosal-to-mucosal Cl- flux; Gt was not affected. In fasted piglets, carbachol increased net Cl- secretion by inhibiting mucosal-to-serosal fluxes with no effect on serosal-to-mucosal fluxes. In addition, carbachol significantly inhibited mucosal-to-serosal Na+ fluxes and reduced Gt in this group. Thus a 48-h fast increased unidirectional and net ion fluxes in piglet jejunum and enhanced ion transport responses to secretory agonists. The mechanism by which carbachol stimulated net Cl- secretion was also altered by the fast. These results suggest that the absence of luminal nutrition changes the ion transport characteristics of the jejunal epithelium.
Carey
H V
HV
Department of Comparative Biosciences, University of Wisconsin School of Veterinary Medicine, Madison 53706.
Hayden
U L
UL
Tucker
K E
KE
D000818:Animals; D000831:Animals, Newborn; D001639:Bicarbonates / Q000494:pharmacology; D001692:Biological Transport; D001835:Body Weight; D002217:Carbachol / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism; D003470:Culture Media; D004594:Electrophysiology; D005215:Fasting / Q000502:physiology*; D005947:Glucose / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000033:anatomy & histology; D007444:Inulin / Q000378:metabolism; D007477:Ions; D007583:Jejunum / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology; D012964:Sodium / Q000378:metabolism; D013268:Stimulation, Chemical; D013552:Swine
D001639:Bicarbonates; D002712:Chlorides; D003470:Culture Media; D007477:Ions; D002217:Carbachol; D007444:Inulin; D012964:Sodium; D005947:Glucose