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.
Department of Physiology, School of Medical Sciences, University of Otago, PO Box 913 Dunedin, New Zealand. grant.butt@stonebow.otago.ac.nz
A G
AG
Butt
S E
SE
Mathieson
B J
BJ
McLeod
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