title: Chloride transport in the rat S1 proximal tubule.
abstract: In vivo microperfusion was used to elucidate the modes and regulation of the powerful chloride transport system resident in the rat early (S1) proximal convoluted tubule (PCT). From a complete, glomerular ultrafiltrate-like perfusate, omission of organic solutes reduced chloride absorption by 93 peq.mm-1.min-1 (302 +/- 10 to 209 +/- 24, P < 0.001). From a high-chloride perfusate (a relatively pure NaCl solution devoid of bicarbonate and organic solutes), luminal addition of the active transport inhibitor cyanide reduced chloride absorption by 153 peq.mm-1.min-1 (632 +/- 17 to 479 +/- 9, P < 0.001). Active transport was also estimated directly as 121 +/- 4 peq.mm-1.min-1 using a solution in which sodium isethionate isosmotically replaced bicarbonate and organic solutes, preventing development of a chloride gradient. Intravenous angiotensin II caused a stimulation of chloride absorption from a high-chloride perfusate by 55 peq.mm-1.min-1 (632 +/- 17 to 687 +/- 14, P < 0.05), which was partially cyanide-sensitive (510 +/- 6 peq.mm-1.min-1). In conclusion, the components of the normal S1 PCT chloride reabsorption (approximately 300 peq.mm-1.min-1) from the glomerular ultrafiltrate consist of the following: active transport (40-50%), which can be regulated by angiotensin II; sodium-coupled organic solute transport (30%); and passive, chloride concentration gradient-driven transport (20-25%).
authors.affiliation: Department of Medicine, University of California, San Francisco, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Wong
authors.forename: C A
authors.initials: CA
authors.lastname: Berry
authors.forename: M G
authors.initials: MG
authors.lastname: Cogan
mesh_terms: D000042:Absorption; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D009995:Osmosis; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002712:Chlorides; D000804:Angiotensin II