AJP - Renal Physiology, Vol 252, Issue 3 374-F381, Copyright © 1987 by American Physiological Society
Thick ascending limb response to dDAVP and atrial natriuretic factor in vivo
L. N. Peterson, C. De Rouffignac, H. Sonnenberg and D. Z. Levine
Because of the inaccessibility of the thick ascending limb (TAL) to
micropuncture, it has been difficult to evaluate the effects of ADH and
atrial natriuretic factor (ANF) on TAL salt transport in vivo. The purpose
of the present study is to assess the effects of these hormones on TAL NaCl
reabsorption in vivo. Although passive NaCl permeability and unidirectional
Na fluxes were not measured, the microstop-flow conductivity technique that
was used in these studies controls solute delivery, permits the measurement
of the rate of net NaCl reabsorption, and tests the capacity of the TAL to
establish a limiting gradient. Despite the presence of a dramatic
natriuretic response, a natural extract of ANF did not significantly
increase the minimum NaCl concentration reached by the TAL after 60 s of
stop-flow. However, 1-[desamino]-8-D-arginine vasopressin (dDAVP) increased
by 23%, the rate at which luminal Na concentration declined, and reduced by
28% the minimum NaCl concentration achieved by the TAL. Therefore, these
results do not demonstrate a significant direct peritubular effect of ANF
on TAL NaCl permeability in outer cortical nephrons, but support a role for
antidiuretic hormone in enhancing TAL NaCl reabsorption in vivo.
