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On the Mechanism of Action of Triamterene: Effects on Transport of Na+, K+, and HVHCO ‐ 3 ‐ions.
Author(s) -
Knauf H.,
Wais U.,
Lübcke R.,
Albiez G.
Publication year - 1976
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.1976.tb00492.x
Subject(s) - triamterene , chemistry , mechanism of action , ion transporter , biophysics , lumen (anatomy) , passive transport , membrane transport , electrolyte , duct (anatomy) , endocrinology , medicine , in vitro , biochemistry , membrane , anatomy , biology , electrode , blood pressure , hydrochlorothiazide
. The rat salivary duct epithelium, which actively transports Na + ., K + ., and H /HCO ‐ 3 in a manner similar to renal distal tubules, was used as a model tissue to study the mechanism of action of triamterene on electrolyte transport. 10 ‐ 4 M triamterene completely blocked Na + resorption and lowered net K + secretion to half that of controls, whereas HCO3 ‐ accumulated in the lumen, probably due to a decrease in H + secretion. The rates of K + and H + /HCO ‐ 3 transport in the presence of triamterene did not differ from those determined after omission of Na + from the luminal fluid. This was considered to be evidence against a direct action of triamterene on transport of K + and HVHCO ‐ 3 . Triamterene rapidly and reversibly reduced the transepithelial electrical potential difference. This was due to almost complete abolition of Na + conductance of the luminal membrane at 10 ‐4 M triamterene, whereas K + conductance was not altered. Triamterene, administered in vitro from the interstitial side of the isolated duct epithelium, was ineffective even at the highest concentrati ons. The activities of the Na–K–ATPase, the Mg‐ATPase and the microsomal HCC^‐ATPase were influenced by 10 ‐4 M triamterene in a similar fashion. These effects were clearly demonstrated only in the homogenate of the duct tissue and not in intact cells in the isolated duct preparation. Therefore they were considered unspecific. The transport studies demonstrate a grimary effect of triamterene on Na + entry from lumen to cell. Influences on net K + and H + /HCO‐ 3 transport are secondary consequences of functional coupling between movement of Na + and movement of K + and H + across the luminal cell membrane.