Differential effects of corticosteroids on Na+ transport in rat distal colon in vitro.
We studied rat distal colon during in vitro incubation with aldosterone and dexamethasone. Both hormones caused short-circuit current (Isc) to increase with a latency period of approximately 3 h. At the 7th h of incubation, control colons had a Isc of 72 +/- 8 microA . cm-2 while tissues incubated with 10(-5) M aldosterone and 10(-8) M dexamethasone, the respective maximal stimulatory concentrations, had similarly increased Isc, 211 +/- 21 and 185 +/- 18 microA . cm-2, respectively. The increase in Isc induced by steroids reflected increased net sodium transport: control, 3.4 +/- 0.8; aldosterone, 6.7 +/- 0.7 (P less than 0.05); and dexamethasone, 7.5 +/- 1.0 mueq . h-1 . cm-2 (P less than 0.025). Spironolactone inhibited the response to both steroids, but the molar ratio of antagonist to agonist was less for aldosterone (approximately 5,000:1) than for dexamethasone (approximately 50,000:1). Amiloride inhibited a greater fraction of aldosterone-induced Isc (0.70 +/- 0.07) than that of dexamethasone (0.37 +/- 0.07; P less than 0.025). The latter value was similar to the effect of amiloride on control tissues (0.35 +/- 0.04). These data provide evidence that the cellular mechanisms by which aldosterone and dexamethasone induce Na+ transport are different.
Jorkasky
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Cox
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Feldman
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D000450:Aldosterone / Q000494:pharmacology*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D004594:Electrophysiology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D013148:Spironolactone / Q000494:pharmacology; D013268:Stimulation, Chemical
D007473:Ion Channels; D013148:Spironolactone; D000450:Aldosterone; D000584:Amiloride; D003907:Dexamethasone; D012964:Sodium