Spironolactone- and canrenone-induced changes in hepatic (Na+,K+)ATPase activity, surface membrane cholesterol and phospholipid, and fluorescence polarization in the rat.
We studied changes in hepatic membrane (Na+,K+)ATPase activity and membrane lipids induced by canrenoate, the water-soluble congener of canrenone, the active metabolite of spironolactone. (Na+,K+)ATPase activity was decreased after canrenoate in a dose- and time-dependent manner. Decreased activity was demonstrated at the lowest dose (91% of control after 5 mumoles per 100 gm body weight per day X 3 days); the maximum dose (30 mumoles per 100 gm body weight per day X 3 days) resulted in activity 38% of untreated control values. A 20 mumoles per 100 gm body weight per day dose decreased enzyme activity to 89 and 55% of control after 24 and 72 hr, respectively. The nonionic detergent Triton WR-1339 partially reversed drug-induced inhibition, suggesting that the enzyme changes may be related to altered membrane lipids. Membrane cholesterol increased 17% after 3 days of 30 mumoles canrenoate per 100 gm body weight per day; phospholipids decreased by 12%. The cholesterol to phospholipid molar ratio increased from 0.419 to 0.555. Membrane fluidity, as measured by the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene decreased after treatment with 20 mumoles canrenoate per 100 gm body weight per day for 3 days. These results describe in vivo and in vitro inhibition of hepatic (Na+,K+)ATPase activity. Increased membrane cholesterol with decreased phospholipid alters membrane fluidity and may be partially responsible for the change in (Na+,K+)ATPase activity.
D000818:Animals; D002192:Canrenone / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005454:Fluorescence Polarization; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects; D010743:Phospholipids / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011245:Pregnadienes / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013148:Spironolactone / Q000494:pharmacology*
D010743:Phospholipids; D011245:Pregnadienes; D013148:Spironolactone; D011092:Polyethylene Glycols; D002192:Canrenone; D002784:Cholesterol; D000254:Sodium-Potassium-Exchanging ATPase