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Aldosterone on sodium transport of rat distal colon in long‐term adrenalectomy during acute and chronic substitution
Author(s) -
Horster Michael,
Lückhoff Andreas
Publication year - 1983
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1983.sp014776
Subject(s) - aldosterone , adrenalectomy , endocrinology , medicine , chemistry , sodium , spironolactone , tonicity , dexamethasone , organic chemistry
1. The influence of aldosterone upon water and sodium transport properties of the distal colon was studied in long‐term adrenalectomy (11‐29 days). 2. Six groups of rats were used: I, normal (control); II, adrenalectomized; III, adrenalectomized, acutely substituted with aldosterone (200 μg/kg 4 h); IV, adrenalectomized rats receiving aldosterone simultaneously with the specific inhibitor spironolactone (40 mg/kg within 4 h); V, adrenalectomized, substituted chronically with aldosterone (2 × 75 μg/kg day); VI, adrenalectomized, substituted chronically with dexamethasone (120 μg/kg day). 3. Distal colon segments were perfused in vivo with isotonic Ringer solution. In addition, a hypotonic electrolyte solution (Na + 111 mM) was used in groups I and II. 4. In adrenalectomy (group II), net water absorption ( J v ) was significantly decreased from (normal) 54·4 μl/h cm 2 ±10·5 ( n = 9) to 41·2 μl/h cm 2 ±7·3 ( n = 4), and net Na + absorption ( J Na ) was decreased from 13·6 μmol/h cm 2 +3·5 to 8·5 μmol/h cm 2 ±0·9 (isotonic perfusate). Similarly, J v was decreased from 54·0 μl/h cm 2 ±8·3 ( n = 4) to 37·3 μl/h cm 2 ±4·2 ( n = 7), and J Na from 8·6 μmol/h cm 2 ±2·1 to 4·2 μmol/h cm 2 ±2·1 (hypotonic perfusate). 5. Acute aldosterone substitution in adrenalectomy (III) had no effect upon J v (37·1 μl/h cm 2 ±10·3; n = 5) but increased J Na to 10·3 μmol/h cm 2 ±0·3. 6. The luminal Na + steady‐state concentration was higher in group II (11·2 mmol l −1 ±3·6; n = 6) than in group I (3·3 mmol l −1 ±1·4; n = 29). Acute aldosterone substitution restored this value to normal (3·0 mmol l −1 ±1·2; n = 4). The aldosterone effect was partly blocked by spironolactone: the Na + steady‐state concentration was 6·4 mmol/l±0·6 ( n = 3) in group IV. 7. At the steady‐state luminal Na + concentration, the osmotically driven net water fluxes were not different in groups I and II, indicating that the hydraulic permeability coefficient is not altered in adrenalectomy. 8. In group V, J v (54·9 μl/h cm 2 ±10·9; n = 7) and J Na (11·9 μmol/h cm 2 ±1·7; n = 6) were not significantly different from normal. 9. In group VI, J v (37·3 μl/h cm 2 ±6·0; n = 5) and J Na (8·0 μmol/h cm 2 ±1·4) were not significantly different from group II. 10. The mineralocorticoid effects of aldosterone in long‐term adrenalectomy appear to represent the principal determining factors of colonic J v and J Na .