Flow-dependence of chloride transport in the rat s1 proximal
tubule.
Wong, Kenneth R., Christine A. Berry, and Martin G. Cogan.
Departments of Medicine and Physiology, University of California
and VA Medical Center, San Francisco, California, 94121
APStracts 2:0084F, 1995.
These studies examined whether the luminal flow-dependency of chloride
absorption in the S1 proximal tubule during glomerulo-tubular 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), an increase in luminal perfusion rate from 30 to 45
nl/min caused stimulation of total chloride absorption (active plus
passive) by 87 (632 +/- 17 to 719 +/- 11, p<0.001) peq/mm_min. When
cyanide was added to this perfusate to eliminate active transport,
the flow-induced change in passive transport was 58 (479 +/- 9 to 537
+/- 11, p<0.001) peq/mm_min. The cyanide-inhibitable, active
transport component was therefore 29 peq/mm_min. With elimination of
the transepithelial chloride gradient and hence passive transport by
isethionate substitution, active transport increased by 63 (121 +/- 4
to 184 +/- 7, p<0.001) peq/mm_min as flow rate rose from 30 to 45
nl/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_min). In conclusion, flow
-dependent active and passive chloride transport in the S1 proximal
tubule may both contribute to normal glomerulo-tubular balance.
Received 20 December 1994; accepted in final form 2 May 1995.
APS Manuscript Number F448-4.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.