Effects of parathyroid hormone on electrolyte transport in the hamster nephron

Harris, Carol; Burnatowska, M. A.; Seely, J. F.; Sutton, R. A.; Quamme, Gary A.; Dirks, JH

doi:10.1152/ajprenal.1979.236.4.f342

Cited by 21 publications

(18 citation statements)

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“…The site of PTH enhancement of magnesium transport has not been as extensively studied. Harris et al (26) demonstrated effects of PTH to enhance magensium reabsorption in the loop of Henle in the thyroparathyroidectomized hamster (26). Similarly, Quamme (6,8) demonstrated PTH-induced magnesium reabsorption when transport had been initially reduced by either hypermagnesemia or furosemide.…”

Section: Resultsmentioning

confidence: 99%

Magnesium transport in the cortical thick ascending limb of Henle's loop of the rabbit.

Shareghi¹,

Agus²

1982

J. Clin. Invest.

138

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A B S T R A C T Isolated cortical thick ascending limbs of Henle's loop were perfused in order to directly evaluate magnesium transport in this segment. Transepithelial potential difference was altered by varying the NaCl concentration in perfusate and bath and adding 50 ,uM furosemide to the perfusate. Perfusion under standard conditions with isotonic solutions resulted in a mean transepithelial potential difference of +8.8±0.7 mV and net magnesium absorption at a rate of 0.32±0.06 pmol/mm per min. Perfusion with a hypotonic solution significantly increased potential difference and the net absorptive rate of magnesium, calcium, and potassium. Conversely, reversal of the polarity of the potential difference with low NaCl bath and luminal furosemide produced net secretion of magnesium, calcium, and potassium. Parathyroid hormone in a bath concentration of 1.0 U/ml increased magnesium absorption from 0.34±0.06 to 0.63±0.06 pmol/mm per min (P < 0.001) and calcium from 0.52±0.08 to 0.97±0.08 pmol/mm per min (P < 0.001). Dibutyryl cyclic AMP produced similar effects on both calcium and magnesium absorption. Increasing bath calcium concentration twofold significantly inhibited net calcium absorption from 0.79±0.27 to 0.16±0.02 pmol/mm per min but magnesium transport was unaffected. Increasing bath magnesium concentration twofold significantly inhibited net magnesium absorption from 0.56±0.14 to -0.09±0.13 pmol/mm per min but had no effect upon net calcium transport. Net absorption of magnesium was significantly increased with increased concentraPortions of this study were presented at the 12th Annual Meeting of the

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Section: Resultsmentioning

confidence: 99%

Magnesium transport in the cortical thick ascending limb of Henle's loop of the rabbit.

Shareghi¹,

Agus²

1982

J. Clin. Invest.

138

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“…1,25(OH) 2 D 3 has been shown to stimulate intestinal absorption of Mg in some but not other studies, and so it may participate in ensuring the availability of sufficient Mg to provide for the body's needs (10,23). In addition, PTH stimulates renal tubular reabsorption of Mg in some species, especially the golden hamster (11). Even without PTH, peritubular (but not luminal) Mg as well as Ca inhibit the reabsorption of both Mg and Ca in the thick ascending limb (TAL) of Henle's loop in the kidney (5).…”

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confidence: 99%

CaSR-mediated interactions between calcium and magnesium homeostasis in mice

Quinn

Thomsen

Egbuna

et al. 2013

American Journal of Physiology-Endocrinology and Metabolism

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Brown EM. CaSR-mediated interactions between calcium and magnesium homeostasis in mice. Am J Physiol Endocrinol Metab 304: E724 -E733, 2013. First published January 29, 2013 doi:10.1152/ajpendo.00557.2012 and magnesium (Mg) homeostasis are interrelated and share common regulatory hormones, including parathyroid hormone (PTH) and vitamin D. However, the role of the calcium-sensing receptor (CaSR) in Mg homeostasis in vivo is not well understood. We sought to investigate the interactions between Mg and Ca homeostasis using genetic mouse models with targeted inactivation of PTH (PTH KO) or both PTH and the calciumsensing receptor (CaSR) (double knockout, DKO). Serum Mg is lower in PTH KO and DKO mice than in WT mice on standard chow, whereas supplemental dietary Ca leads to equivalent Mg levels for all three genotypes. Mg loading increases serum Mg in all genotypes; however, the increase in serum Mg is most pronounced in the DKO mice. Serum Ca is increased with Mg loading in the PTH KO and DKO mice but not in the WT mice. Here, too, the hypercalcemia is much greater in the DKO mice. Serum and especially urinary phosphate are reduced during Mg loading, which is likely due to intestinal chelation of phosphate by Mg. Mg loading decreases serum PTH in WT mice and increases serum calcitonin in both WT and PTH KO mice but not DKO mice. Furthermore, Mg loading elevates serum 1,25-dihydroxyvitamin D in all genotypes, with greater effects in PTH KO and DKO mice, possibly due to reduced levels of serum phosphorus and FGF23. These hormonal responses to Mg loading and the CaSR's role in regulating renal function may help to explain changes in serum Mg and Ca found during Mg loading. calcium-sensing receptor; calcium; magnesium; parathyroid hormone; 1,25-dihydroxyvitamin D 3; calcitonin; osteocalcin; alkaline phosphatase; deoxypyridinoline MAGNESIUM (Mg) is an essential divalent cation that has a plethora of roles in the body, particularly intracellularly, where it participates in energy metabolism and intracellular signaling through its involvement in multiple phosphorylation reactions. Not surprisingly, the level of extracellular Mg is maintained within a relatively narrow range of ϳ0.75-1.05 mmol/l. This is slightly lower than the level at which extracellular calcium (Ca) is maintained (serum ionized Ca ϭ ϳ1.1-1.3 mmol/l). Extracellular Ca homeostasis comprises three key elements: 1) tissues that transport Ca into or out of the extracellular fluid (kidney, bone, and intestine), 2) hormones that regulate these fluxes {e.g., parathyroid hormone (PTH), 1,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ], calcitonin (CT), and fibroblast growth factor 23 (FGF23)}, and 3) one or more Ca sensors [viz., the calcium-sensing receptor (CaSR)] that measure the level of Ca in the blood and regulate the secretion of Ca-regulating hormones or Ca fluxes themselves (e.g., in the kidney) (3).Less is known about the mechanisms underlying the maintenance of Mg homeostasis than of Ca homeostasis, although there have been recent important advances in th...

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“…In the proximal convoluted tubule, where Ca2+ transport is isotonic and generally associated with fluid and Na+ fluxes (1)(2)(3)(4), PTH has been shown to inhibit solute reabsorption isotonically (16)(17)(18)(19), or alternatively to have no effect on Ca2+ reabsorption (20,21). In the hamster, Harris et al (13) nephron is unclear. In some respects, the effect of PTH on proximal tubular solute reabsorption is similar to procedures which decrease peritubular Na+ concentrations or are presumed to increase cytosolic Ca2" (23).…”

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confidence: 99%

Calcium transport in canine renal basolateral membrane vesicles. Effects of parathyroid hormone.

Scoble¹,

Mills²,

Hruska³

1985

J. Clin. Invest.

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IntroductionThe effects of parathyroid hormone were studied on Ca" fluxes in canine renal proximal tubular basolateral membrane vesicles (BLMV). Efflux of Ca2+ from preloaded BLMV was found to be stimulated by an external Na' gradient, and this was inhibited by the Na' ionophore, monensin, and enhanced by intravesicular negative electrical potentials, which indicated electrogenic Na+/Ca2" exchange activity. There was a Na' gradient independent Ca2+ flux, but membrane binding of Ca2" was excluded from contributing to the Na' gradient-dependent efflux. The Na' gradient-dependent flux of Ca2" was very rapid, and even 2-and 5-s points may not fully represent absolute initial rates. It was saturable with respect to the interaction of Ca2" and Na' with an apparent (5 s) K. for Na'-dependent Ca2" uptake of 10 ,uM, and an apparent (5 s) V.,.,, of 0.33 nmol/mg protein per 5 s. The Na' concentration that yielded half maximal Ca2" efflux (2 s) was 11 mM, and the Hill coefficient was two or greater. Both Na+ gradient dependent and independent Ca2" efflux were decreased in BLMV prepared from kidneys of thyroparathyroidectomized (TPTX) dogs, and both were stimulated by parathyroid hormone (PTH) infusion to TPTX dogs. BLMV from TPTX dogs exhibited significantly reduced maximal stimulation of Na+ gradient-dependent Ca2+ uptake with an apparent (5 s) V,,, of 0.23 nmol/mg protein per 5 s, but the apparent K. was 8 ,uM, which was unchanged from normal. The Na+ gradient independent Ca2+ uptake was also reduced in BLMV from TPTX dogs compared with normal. Thus, PTH stimulated both Na+/Ca2" exchange activity and Na+ independent Ca2" flux. In vivo, the latter could result in an elevation of cytosolic Ca2" by PTH, and this might contribute to the observed decrease in solute transport in the proximal tubule. (33). Renal medullary tissue was removed from the kidneys, and renal cortical tissue was diced and homogenized using a Potter-Elvehjem Teflon homogenizer in homogenizing buffer (250 mM sucrose, 20 mM Tris base, and 1 mM EGTA adjusted to pH 7.6), 20 ml/g of tissue.The suspension was then further homogenized using a Polytron homogenizer (Brinkman Instruments, Westbury, NY), setting six for three bursts of 30 s. After samples were taken for analysis of protein and enzyme content, the homogenate was centrifuged at 2,500 g for 15 min and the pellet discarded. The suspension was then spun at 24,000 g for 20 min and the supernatant decanted. The soft portion of the pellet was resuspended in the homogenizing buffer to a value of 1.3 ml/g initial tissue and hand homogenized for seven strokes with a Dounce homogenizer. The suspension was then diluted and thoroughly mixed with 1.6 ml/g initial tissue of 100% Percoll (Pharmacia Fine Chemicals, Upsala, Sweden) and the homogenizing buffer, 17 ml/g initial tissue (final Percoll concentration 8%). The suspension was then centrifuged at 30,000 g for 35 min. This produced a density gradient of Percoll from 1.005 to 1.125 g/ml. The fraction corresponding to an opaque band and density 1.030-1...

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Effects of parathyroid hormone on electrolyte transport in the hamster nephron

Cited by 21 publications

References 0 publications

Magnesium transport in the cortical thick ascending limb of Henle's loop of the rabbit.

Magnesium transport in the cortical thick ascending limb of Henle's loop of the rabbit.

CaSR-mediated interactions between calcium and magnesium homeostasis in mice

Calcium transport in canine renal basolateral membrane vesicles. Effects of parathyroid hormone.

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