PT  - JOURNAL ARTICLE
AU  - S Nowicki
AU  - J A Opezzo
AU  - G Levin
AU  - D Gonzalez
AU  - M M Elias
TI  - Furosemide renal excretion rate and the effects of the diuretic on different tubular sites are modified by endogenous dopamine in normohydrated rats.
DP  - 1995 Sep 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1348--1354
VI  - 274
IP  - 3
4099  - http://jpet.aspetjournals.org/content/274/3/1348.short
4100  - http://jpet.aspetjournals.org/content/274/3/1348.full
SO  - J Pharmacol Exp Ther1995 Sep 01; 274
AB  - The present study was designed to explore the involvement of endogenous dopamine in furosemide excretion and in the actions of the diuretic on tubular sodium reabsorption. The dose-response relationship for the diuretic effect of furosemide given as i.v. bolus injections (0.2-7.5 mg.kg-1) was studied by clearance technique in pentobarbital-anesthetized rats treated with vehicle, benserazide (BZ) (25 mg.kg-1 i.v.) or SCH 23390 (50 micrograms.kg-1 + 10 micrograms.kg-1.min-1 i.v.). Furosemide induced the maximal diuresis 15 to 30 min after i.v. administration. The diuretic response was dose-dependent and was reduced in the animals treated with BZ and SCH 23390. Fractional sodium excretion was also increased by furosemide from 1.8 to 7.5% during the same period. This effect was reduced by both BZ or SCH 23390 by 35 to 50%. The effects of furosemide on proximal and distal renal tubules were dissected by measuring the renal lithium clearance (CLi+). Furosemide effective on proximal tubular sites (measured by FENa+ prox = CLi+/Cln) were completely abolished by BZ and SCH 23390, whereas both drugs reduced furosemide effects on distal tubular sites (measured by FENa+ distal = CNa+/CLi+) by 20 to 40%. Furosemide excretion rate during the peak response to the diuretic was measured in the urine. BZ and SCH 23390 diminished furosemide excretion by 45 to 80% as compared with vehicle-treated animals. The furosemide tubular effects and the proximal and distal functions measured by CLi+ determined during the peak response were correlated to the maximal excretion rate of furosemide in the urine.(ABSTRACT TRUNCATED AT 250 WORDS)