title: Amiloride effect on diurnal cyclic Na and K excretion in rats.
abstract: Amiloride was administered to rats during the peak and minimum of Na and K diurnal rhythmic excretion (i.e., during early dark phase and early light phase). In rats receiving a normal-K diet (2.34 meq/day) amiloride decreased K excretion from 186 to 37 mueq/h (dark phase) and from 31 to 4 mueq/h (light phase). Amiloride increased Na excretion from 91 to 344 mueq/h (dark phase) and from 35 to 164 mueq/h (light phase). Rats receiving a high-K diet (10.4 meq/day) showed a higher diurnal peak and minimum for K excretion. During high-K intake, amiloride decreased K excretion from 787 to 191 mueq/h (dark phase) and from 197 to 40 mueq/h (light phase) and increased Na excretion from 237 to 891 mueq/h (dark phase) and from 31 to 222 mueq/h (light phase). Whenever given, amiloride reduced K excretion to approximately 20% of control excretion. It is concluded that rhythmic changes in amiloride-sensitive distal transport are largely, but not entirely, responsible for the diurnal K cycle, but do not cause the concurrent Na cycle. Thus the diurnal cycles in Na and K are expressed through changes in different transport mechanisms. In rats maintained on a high-K diet there is an increase in rhythmic K secretion and Na reabsorption by amiloride-sensitive transport. To maintain Na excretion unchanged, Na reabsorption must be correspondingly depressed at an amiloride-insensitive site.
authors.affiliation: Department of Human Physiology, University of California School of Medicine, Davis 95616.
authors.forename: P L
authors.initials: PL
authors.lastname: Dalton
authors.forename: L
authors.initials: L
authors.lastname: Rabinowitz
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D003624:Darkness; D008027:Light; D008297:Male; D011188:Potassium / Q000652:urine*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012964:Sodium / Q000652:urine*
chemical_list: D000584:Amiloride; D012964:Sodium; D011188:Potassium