Stimulation by glucagon and PTH of Ca and Mg reabsorption in the superficial distal tubule of the rat kidney

Abstract

The effects of glucagon and PTH on electrolyte reabsorption in the distal tubule were investigated in rats deprived of vasopressin, calcitonin, PTH, and glucagon. Micropunctures of distal tubule, at a late and an early site of a same nephron, have been performed in 23 rats, nine control, seven infused with glucagon (5 ng X min-1 X 100 g-1 b.w.) and seven with PTH (5 mU X min-1 X 100 g-1 b.w.). The Ca and Mg reabsorptive capacity of the distal segment was increased by glucagon and by PTH. Moreover, fractional Na and Cl reabsorption was significantly higher than in control during PTH administration. A K secretion appeared during the administration of both hormones. No phosphate net transport was observed in any group. Finally, the data presented here, together with those previously reported, indicate that the increase of Ca and Mg renal reabsorption observed with glucagon and PTH results from an effect located in both Henle's loop, where the bulk of Ca and Mg is reabsorbed, and the distal tubule.

The hypomagnesaemic action of FK506: urinary excretion of magnesium and calcium and the role of parathyroid hormone

“…an increase in the lumen-positive potential), thereby increasing magnesium absorption via the paracellular pathway [6]. In the distal tubule, where transcellular magnesium absorption occurs [6], micropuncture studies have demonstrated that PTH also significantly increases magnesium transport [7].…”

Sensitivities of rat kidney thick ascending limbs and collecting ducts to vasopressin in vivo.

“…Free access to distilled water was available until anesthesia. The animals were prepared in order to reduce the plasma concentration of calcitonin, PTH, and glucagon (6)(7)(8)(9)(10)(11). They are called hormone-deprived animals throughout this paper.…”

“…The response ofthe collecting ducts was evaluated by the changes in urine flow. Calcitonin, parathyroid hormone (PTH), and glucagon may act on Mg2+ reabsorption in the distal tubule (7,8) and the thick ascending limb (9,10), and calcitonin may act in the same way as [Arg8]vasopressin on the permeability of the cortical collecting duct to water (11,12). To avoid undesirable interference from these hormones, the experiments were performed with hormone-deprived rats (4); i.e., Brattleboro D. I. rats (lacking [Arg8]vasopressin) that were acutely thyroparathyroidectomized (thus suppressing calcitonin and PTH levels) and given somatostatin to inhibit glucagon secretion (6)(7)(8)(9)(10)(11).…”

Effect of Magnesium Infusion on Calcium Handling in the Rat Kidney

“…There is already evidence (Quamme, 1982) that hypercalcaemia reduces reabsorption of both calcium and magnesium at this site and that here is interaction between the reabsorptive processes for the two cations (Quamme & Dirks, 1980). Glucagon and PTH stimulate reabsorption of both cations (Bailly, Roinel & Amiel, 1985) as does calcitonin (Di Stefano, Elalouf, Garel & de Rouffignac, 1985). The mechanism of magnesium reabsorption by the loop of Henle is not known although it appears to be related to sodium chloride transport, possibly via changes in intratubular potential difference (Quamme, 1986).…”