Stimulation of tubular reabsorption of magnesium and calcium by antidiuretic hormone in conscious rats. Study in Brattleboro rats with hereditary hypothalamic diabetes insipidus
Bouby, N.; Trinh-Trang-Tan, M.M.; Bankir, L.
Pflugers Archiv European Journal of Physiology 402(4): 458-464
1984
ISSN/ISBN: 0031-6768 PMID: 6522252 Document Number: 240135
The effect of antidiuretic hormone ), for Ca: 2.92 .+-. 0.62 and 0.34 .+-. 0.05% (P < 0.001) and for Mg: 7.75 .+-. 0.83 and 1.38 .+-. 0.28% (P < 0.001). After treatment discontinuation, plasma osmolality in group E rose to 304 .+-. 2 mosmol/kg H2O (P < 0.01 compared to period A) with slight increases in plasma Na and Cl concentrations. Urine osmolality fell below, and urine flow rate rose above values observed in the control group. Fractional excretion of Ca and Mg rose to values seen in DI rats (3.30 .+-. 0.37%, Ns, for Ca) or above (26.95 .+-. 0.65%, P < 0.001, for Mg), with no change in other solute fractional excretion. Long-term exposure to dDAVP induces a marked hypertrophy of the epithelium of the thick ascending limb of Henle's loop in its medullary part (MTAL). dDAVP induces an increase in Ca and Mg tubular reabsorption between end proximal and early distal sites of micropuncture. The effects of ADH on divalent cation fractional excretion, seen in the present study, probably results from an increased Ca and Mg voltage-dependent reabsorption in the MTAL. This reabsorption is linked to the increased salt transport induced in this segment, both by a direct effect of ADH and by an indirect effect resulting from the increased solute delivery to the MTAL in the concentrating kidney.