title: Flow dependence of chloride transport in rat S1 proximal tubules.
abstract: These studies examined whether the luminal flow dependency of chloride absorption in the S1 proximal tubule during glomerulotubular balance was due to change in active and/or passive transport of chloride. Using in vivo microperfusion in the Munich-Wistar rat and an essentially pure sodium chloride perfusate (devoid of bicarbonate and organic solutes), we found that an increase in luminal perfusion rate from 30 to 45 nl/min caused stimulation of total chloride absorption (active plus passive) by 87 peq.mm-1.min-1 (632 +/- 17 to 719 +/- 11, P < 0.001). When cyanide was added to this perfusate to eliminate active transport, the flow-induced change in passive transport was 58 peq.mm-1.min-1 (479 +/- 9 to 537 +/- 11, P < 0.001). The cyanide-inhibitable active transport component was therefore 29 peq.mm-1.min-1. With elimination of the transepithelial chloride gradient and, hence, passive transport by isethionate substitution, active transport increased by 63 peq.mm-1.min-1 (121 +/- 4 to 184 +/- 7, P < 0.001) as flow rate rose from 30 to 45nl/min. Removal of organic solutes from a glomerular ultrafiltrate-like perfusate had a minimal effect on flow-induced change in chloride transport (190 vs. 207 peq.mm-1.min-1). In conclusion, flow-dependent active and passive chloride transport in the S1 proximal tubule may both contribute to normal glomerulotubular balance.
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; D000818:Animals; D001692:Biological Transport; D001693:Biological Transport, Active; D002712:Chlorides / Q000493:pharmacokinetics*; D007678:Kidney Glomerulus / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000502:physiology*; D008297:Male; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride
chemical_list: D002712:Chlorides; D012965:Sodium Chloride