Hormonal regulation of sodium-fluid balance and some hemodynamic parameters in the rat. II. The effect of sodium depletion and sodium loading on rats with inherited diabetes insipidus (Brattleboro strain).

The effect of furanthril after an acute (24 hours) and chronic administration (7 days), and the effect of 7-days sodium loading was followed on control Long Evans (LE) and Brattleboro rats with inherited hypothalamic diabetes insipidus (DI). In addition to the routine sodium-fluid balance study, plasma renin activity and prostaglandins excretion were examined. In control LE rats was found a typical diuretic- and natriuretic effect of furanthril only after an acute (14 hours) administration of the drug. This effect was attributed to the stimulation of renal PGE2 synthesis. In sodium-depleted state (7 days after administration of furanthril) the diuretic- and natriuretic effect was missing due to the extensive sodium deficit. In DI rats was found a paradoxical antidiuretic effect of furanthril after either an acute or chronic treatment, which was attributed to the per se stimulated renin-angiotensin system and suppressed PG-synthesis typical for these rats. The conclusion of this studies was that an availability of ADH is necessary for PG-response to sodium depletion. After sodium loading, an exaggerated natriuresis, decreased PRA, and depressed PG-synthesis was found in DI rats. The feedback mechanism between renin axis and prostaglandin system in the absence of ADH was discussed.