AJP - Renal Physiology, Vol 249, Issue 2 291-F298, Copyright © 1985 by American Physiological Society
Effects of dDAVP on rat juxtamedullary nephrons: stimulation of medullary K recycling
J. M. Elalouf, N. Roinel and C. de Rouffignac
The effects of 1-desamino-8-D-arginine vasopressin (dDAVP) on the handling
of water and electrolytes by the juxtamedullary nephrons were studied on
rats with reduced circulating levels of antidiuretic hormone (ADH),
parathyroid hormone, calcitonin, and glucagon, all of which stimulate the
adenylate cyclase system of the thick ascending limb and the distal tubule.
In such hormone-deprived rats and in hormone-deprived + dDAVP rats, the
concentration of Na, Cl, and total solutes was lower in the ascending than
in the descending limbs, whereas the inulin concentration was similar at
both sites. dDAVP did not alter the fraction of NaCl remaining in the thin
limbs, but tended to reduce that of Mg and Ca. On the other hand, dDAVP
significantly increased the fraction of filtered K remaining from 65.8 +/-
5.2 to 107.3 +/- 15.8%. A direct correlation was observed between the
fraction of filtered K remaining at the tip of the juxtamedullary loops and
the fractional excretion rate of K in urine. Since dDAVP enhances distal K
net secretion, as previously shown in our laboratory, these results
indicate that the medullary recycling of K from nephron terminal segments
to Henle's loop of juxtamedullary nephrons is stimulated by this peptide.
