title: Atrial peptide and cGMP effects on NaCl transport in inner medullary collecting duct.
abstract: We examined the action of atrial natriuretic factor (ANF) on Na+ and Cl- transport in in vitro microperfused inner medullary collecting ducts (IMCD) isolated from rat kidneys. First we studied the isotopic fluxes at low perfusion rates (7 nl/min). The results showed that ANF added to bath decreased lumen-to-bath flux (Jl----b) of Na+ and increased Na+ bath-to-lumen flux (Jb----l). This was substantiated by a direct demonstration that ANF reduces net Na+ and Cl- absorption. The effect of ANF on Jl----b and Jb----l of Na+ was also observed at high perfusion rates (25 nl/min). The inhibitory effect of ANF was observed even when Na+ Jl----b was stimulated by vasopressin (VP). ANF (6 x 10(-11) M) added to bath increased Cl- Jb----l and generated a negative lumen potential difference (PD). These two effects were inhibited by furosemide and by the replacement of Na+ by choline and Cl- by SO4(2-) in the bath fluid. These observations are compatible with the existence of a Na(+)-Cl(-)-K+ cotransport mechanism stimulated by ANF. Moreover, the effects of guanosine 3',5'-cyclic monophosphate (cGMP) added to the bath on PD, Jl----b, and Jb----l of Na+ were similar to those observed with ANF. Thus, physiological concentrations of ANF inhibit directly Na+ and Cl- absorption in IMCD by two mechanisms, 1) by increasing cotransport Na(+)-Cl(-)-K+ secretion and 2) by inhibiting NaCl absorption both in the absence and in the presence of VP. These effects on NaCl transport appear to be mediated by cGMP.
authors.affiliation: Departamento de Clínica Médica, Faculdade de Medicina, Universidade de São Paulo, Brazil.
authors.forename: A S
authors.initials: AS
authors.lastname: Rocha
authors.forename: L H
authors.initials: LH
authors.lastname: Kudo
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D006152:Cyclic GMP / Q000494:pharmacology*; D004594:Electrophysiology; D007679:Kidney Medulla; D007684:Kidney Tubules / Q000378:metabolism* / Q000502:physiology; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters
chemical_list: D002352:Carrier Proteins; D002712:Chlorides; D028021:Sodium-Potassium-Chloride Symporters; D012965:Sodium Chloride; D009320:Atrial Natriuretic Factor; D012964:Sodium; D006152:Cyclic GMP