title: [Inhibition of sodium transport in the colon by the diuretic amiloride (author's transl)].
abstract: In isolated epithelia of rabbit descending colon the short-circuit current (Isc) is solely attributable to net transepithelial Na-transport, which in turn is identical with the unidirectional Na-influx across the luminal cell membranes. Amiloride blocks Isc by inhibiting luminal Na-influx into the cells. The type of inhibition exerted by amiloride in this tissue has to be termed mixed-type, since both the affinity of Na to its transport system and the maximal transport capacity are reduced. Na, on the other hand, is a competitive antagonist of the amiloride effect with a Ki of 136 mM; therefore KA, the amiloride-concentration at which the amiloride-effect is half-maximal, is increased from 0.14 microM at 5 mM Na in the incubation medium to 0.29 microM at 140 mM Na. It is conceivable that an "amiloride-like" action of Na may be responsible for the saturability of luminal Na-influx with increasing Na-concentrations.
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D066298:In Vitro Techniques; D011719:Pyrazines / Q000494:pharmacology*; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*
chemical_list: D011719:Pyrazines; D000584:Amiloride; D012964:Sodium
vernacular_title: Hemmung des Natriumtransports im Colon durch das Diuretikum Amilorid.