title: Thyroid hormone-aldosterone interaction on Na+ transport in toad bladder.
abstract: Repeated administration of thyroxine (T4) in vivo (2 microgram/100 g body wt for 6 days) lowered by 2.3 times (P less than 0.025, df = 18) the basal rate of Na+ transport measured by the short-circuit current (SCC) in vitro in the urinary bladder of the toad (Bufo marinus). This difference was not accounted for by a change in the plasma aldosterone concentration. Moreover the response of the SCC to aldosterone in vitro was markedly inhibited in bladders from T4-treated animals (P less than 0.001, df = 18). These findings raised the possibility of a direct interaction between thyroid hormone and aldosterone in the target cell. The effects of L-triiodothyronine (T3) and aldosterone were examined in vitro. T3 alone (60 nM) had no significant effect on the base-line SCC (deltamuA = -14 +/- 11 (SE) muA per hemibladder; P greater than 0.3, n = 10). By contrast, T3 (60 nM) inhibited the response of the SCC to aldosterone from 6 to 8 h after its addition (deltamuA = -98 +/- 19 muA per hemibladder; P less than 0.001, n = 10). The inhibition by T3 was present at 6 nM (P less than 0.01, n = 10) and became not significant at 0.6 nM. T3 had no significant effect on base-line or aldosterone-stimulated H+ transport. Thyroid hormone might therefore regulate the late response of the SCC to aldosterone at the level of its target cell.
mesh_terms: D000450:Aldosterone / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002024:Bufo marinus / Q000378:metabolism; D004359:Drug Therapy, Combination; D005260:Female; D008297:Male; D012964:Sodium / Q000378:metabolism*; D013974:Thyroxine / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology*; D001743:Urinary Bladder / Q000378:metabolism*
chemical_list: D014284:Triiodothyronine; D000450:Aldosterone; D012964:Sodium; D013974:Thyroxine