Aldosterone does not regulate amiloride-sensitive Na(+) transport in the colon of the Australian common brushtail possum, Trichosurus vulpecula.
Plasma aldosterone concentrations and the magnitude of amiloride-sensitive Na(+) transport in the proximal and distal colon of newly caught wild possums, and of possums maintained on either low or high Na(+) diets, were determined to evaluate their role in the regulation of salt content of faeces in common brushtail possums. Wild animals had a plasma aldosterone concentration of 439+/-115 pmol l(-1) and high levels of amiloride-sensitive Na(+) transport in both the proximal and distal colon. Animals maintained on a low Na(+) diet for 14 days excreted very little Na(+) in the urine and had an elevated aldosterone concentration (840+/-246 pmol l(-1)), but levels of amiloride-sensitive Na(+) transport in the proximal and distal colon were similar to those in wild animals. Conversely, while provision of a high Na(+) diet (7 days or 14 days) resulted in increased urinary Na(+) excretion and a fall in aldosterone (approximately 250 pmol l(-1)), there was no reduction in the amount of amiloride-sensitive Na(+) transport in either the proximal or distal colon. These data strongly indicate that aldosterone does not regulate amiloride-sensitive Na(+) transport in the colon of possums and that the colon is not involved in the regulation of salt content of the faeces in this species.
Butt
A G
AG
Department of Physiology, School of Medical Sciences, University of Otago, PO Box 913 Dunedin, New Zealand. grant.butt@stonebow.otago.ac.nz
Mathieson
S E
SE
McLeod
B J
BJ
D000450:Aldosterone / Q000502:physiology*; D000584:Amiloride / Q000097:blood*; D000821:Animal Feed; D000818:Animals; D000835:Animals, Wild / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology; D003106:Colon / Q000378:metabolism* / Q000502:physiology; D004039:Diet, Sodium-Restricted; D004553:Electric Conductivity; D008297:Male; D009318:Natriuresis; D009893:Opossums / Q000378:metabolism*; D011188:Potassium / Q000652:urine; D012964:Sodium / Q000378:metabolism*
D000450:Aldosterone; D000584:Amiloride; D012964:Sodium; D011188:Potassium