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Query: UMLS:C0020437 (hypercalcemia)
 10,293 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cardiac Na+,K(+)-ATPase, the receptor molecule for digitalis glycosides, have isoforms with different intrinsic affinities for the glycosides. Expression of these isoforms are under developmental and hormonal regulation. Switching in isoforms to those with lower intrinsic affinity may decrease digitalis sensitivity of the heart. In addition to the intrinsic affinity of the cardiac Na+,K(+)-ATPase for the glycoside, increases in the rate of Na+ influx and decreases in extracellular K+ concentrations increase glycoside sensitivity of the heart and also reduces the margin of safety by reducing reserve capacity of the sodium pump. Reserve capacity of the sodium pump is also reduced by pathological conditions or aging, resulting in reduced margin of safety for the glycoside. Events that follow sodium pump inhibition also affect sensitivity of the heart to digitalis toxicity. These are hypercalcemia and magnesium depletion. It is now feasible to predict digitalis sensitivity of the heart, not empirically but based on the understanding of the mechanisms responsible for the positive inotropic and toxic actions of the glycoside.
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PMID:Digitalis sensitivity of Na+,K(+)-ATPase, myocytes and the heart. 184 28

Total serum calcium concentration was raised in a 63-year-old lady with multiple myeloma and markedly elevated serum IgA kappa-paraprotein concentration. Symptoms of hypercalcaemia were absent, and serum ionized calcium was normal, suggesting calcium binding by the abnormal protein. This was demonstrated directly after isolation of the paraprotein and characterization of the calcium/protein interaction. After reduction of the paraprotein with mercaptoethanol, sodium dodecyl sulphate polyacrylamide gradient gel electrophoresis revealed two bands corresponding to light and heavy chains, but under non-reducing conditions the isolated paraprotein migrated in a series of bands, possibly representing polymeric forms of the basic immunoglobulin moiety.
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PMID:Hypercalcaemia due to calcium binding by a polymeric IgA kappa-paraprotein. 187 67

The management of hypercalcemia of malignancy is guided by assessments of its various components. Since the intestine usually makes no contribution to hypercalcemia under these circumstances, the problem is to measure the net efflux of calcium out of bone and the ability of the kidneys to excrete the unwanted calcium load. Established relationships between serum and urinary calcium excretion rates allow the quantitation of the relative contribution of an impaired glomerular filtration rate, of reduced renal tubular calcium reabsorption, and of increased bone resorption. Since the renal handling of calcium is closely related to that of sodium in the proximal nephron, the rate of sodium excretion is an important variable in these measurements. A practical approach to the separation of hypercalcemia into its renal and skeletal components is described in this article. Examples of how these measurements can be used to assess the responses to various types of therapy for malignancy-associated hypercalcemia are also given.
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PMID:Assessment of renal and skeletal components of hypercalcemia. 210 28

In studies in conscious dogs, 1 liter 0.3% calcium chloride infusion resulted in a 163% increase in serum ionized calcium (iCa2+), 166% increase in plasma immunoreactive atrial natriuretic peptide (irANP) and 33% increase in mean blood pressure with significant positive correlation between serum iCa2+ and plasma irANP levels. Pretreatment with verapamil reversed the effects of calcium infusion. These studies have demonstrated that calcium ions play an important role in ANP secretion with reversal by calcium antagonist, verapamil. Hyponatremia seen with calcium infusion could reflect calcium-enhanced sodium excretion. Hypercalcemia was accompanied by non-significant changes in plasma renin activity and significantly elevated serum aldosterone not reversed by verapamil.
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PMID:Influence of calcium infusion on plasma atrial natriuretic peptide in conscious dogs: intervention with calcium antagonist, verapamil. 215 Sep 76

The PTH-like peptide (PTHLP) responsible for hypercalcemia in many patients with humoral hypercalcemia of malignancy (HHM) acts on PTH receptors in bone and kidney, and large doses of PTHLPs have been shown to reduce urinary calcium excretion. However, PTHLPs have not been assessed quantitatively for effects on renal calcium excretion at concentrations (5-100 pM) now known to be found in the serum of patients with HHM. We perfused isolated rat kidneys with synthetic [tyr-36] PTHLP-(1-36)amide [PTHLP-(1-36)], PTHLP-(1-74), and synthetic bovine PTH-(1-34). The ratio of calcium to sodium clearances (CCa/CNa), a measure of distal tubular calcium transport, was reduced to the same extent by PTH, PTHLP-(1-36), and PTHLP-(1-74) (54.3 +/- 3.9, 52.9 +/- 3.9, and 52.7 +/- 1.3% reductions from control), respectively) at maximal doses (35-50 pM and higher), with half-maximal effects at 10, 18, and 32 pM, respectively. PTH, PTHLP-(1-36), and PTHLP-(1-74) all increased fractional phosphate excretion over control (p less than 0.05 each). All three peptides were natriuretic, at least doubling fractional Na excretion (p less than 0.05 or less). Urinary cAMP excretion was increased by all three. None had any effect on GFR or renal vascular resistance. These results indicate that clinically relevant concentrations of PTHLPs are anticalciuretic and natriuretic, with maximal effects similar to those of PTH. Differences in anticalciuretic potencies are small but may explain differences among patients, depending on the size(s) and concentrations of the native circulating form(s) of the peptide.
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PMID:Quantitative evaluation of anticalciuretic effects of synthetic parathyroid hormonelike peptides. 216 24

The isolated perfused rat kidney was used to study the effects of amino-terminal fragments of human parathyroid hormone, hPTH(1-34), bovine parathyroid hormone, bPTH(1-84) and of PTH-related proteins, PTHrP(1-34), PTHrP(1-84), PTHrP(1-108) and PTHrP(1-141) on urinary bicarbonate excretion. PTHrP(1-34) (7 nmol/l), bPTH(1-84) (5.5 nmol/l) and hPTH(1-34) (7 nmol/l) had similar effects in increasing bicarbonate excretion with respect to the control. At lower concentrations (0.7 nmol/l) all PTHrP components, but not hPTH(1-34) or bPTH(1-84) increased bicarbonate excretion significantly. Infusions of PTHrP(1-108) and PTHrP(1-141) at 0.7 nmol/l, while associated with a rise in urinary bicarbonate concentration and excretion during the early stages of perfusion, produced a sharp decline in bicarbonate concentration and excretion in the latter part of perfusion. The different peptides produced no significant differences in glomerular filtration rate, fractional excretion of sodium or urine volume. The absence of substantial differences between the effects of hPTH(1-34) and PTHrP(1-34) are as noted in previous studies. The differences between PTHrP(1-108)/PTHrP(1-141) and PTHrP(1-34) demonstrated here are consistent with (1) the clinical manifestations of acidosis in hyperparathyroidism and alkalosis in humoral hypercalcaemia of malignancy, and (2) an independent action of a component of PTHrP beyond amino acids 1-34.
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PMID:Comparison of the effects of parathyroid hormone (PTH) and recombinant PTH-related protein on bicarbonate excretion by the isolated perfused rat kidney. 221 31

Nine patients with primary hyperparathyroidism were studied to investigate the renal tubular reabsorption of calcium and sodium. Fasting serum and urine samples were analysed, and the glomerular filtration rate and the renal plasma clearance of lithium were determined simultaneously. Comparison was made with 9 age- and sex-matched normocalcemic controls. In the proximal tubule, there was a significantly higher absolute reabsorption of calcium in patients than in controls, whereas the fractional reabsorption rate of calcium did not differ between the two groups. In the distal tubule, the absolute calcium reabsorption rate was significantly higher in the patients, whereas the fractional reabsorption rate of calcium was significantly lower than in controls. In the patient group there was a significantly positive linear correlation between the increased tubular capacity for calcium reabsorption and the absolute proximal calcium reabsorption rate, but not between the increased capacity and the absolute distal calcium reabsorption rate. No significant differences were found in the renal tubular handling of sodium between patients and controls. Our results suggest that the increased capacity for tubular calcium reabsorption in primary hyperparathyroidism mainly is localized in the proximal tubule, and that the renal tubular handling of calcium and sodium in this disease differs from that in familial hypocalciuric hypercalcemia.
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PMID:Renal tubular reabsorption of calcium and sodium in primary hyperparathyroidism. 222 Feb 60

Some patients treated for the hypercalcaemia of malignancy develop renal tubular resistance to the effects of calcitonin which is independent of concurrent changes in sodium excretion. This type of resistance can be overcome by the addition of corticosteroids. In other patients apparent renal resistance to calcitonin is a consequence of reduced sodium excretion and is unaffected by corticosteroids.
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PMID:Potentiation of calcitonin by corticosteroids during the treatment of the hypercalcaemia of malignancy. 232 45

Prolactin (PRL) was purified from chum salmon, Oncorhynchus keta, pituitary glands and was used to develop a homologous radioimmunoassay for the measurement of PRL from salmon. The plasma PRL response to freshwater (FW) transfer differed in seawater (SW)-adapted postsmolt (250 g) and smolts (15 g) of coho salmon. Postsmolts had a pronounced and prolonged elevation of plasma titers of PRL with hypercalcemia and stable plasma sodium levels. The FW-transferred postsmolts had significantly lower pituitary gland PRL only at 0.5 and 2 hr post-transfer as compared to SW-SW. Smaller smolts showed stable plasma PRL levels after FW transfer, hypocalcemia 48 post-transfer, depressed plasma sodium concentrations, and lowered plasma osmotic pressure. This different response may be due to an increased osmoionic regulatory challenge encountered by the smaller smolts or possibly due to some other developmental change between the two different age classes.
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PMID:Differential response of plasma prolactin to freshwater transfer of smolts and postsmolts of seawater-adapted coho salmon (Oncorhynchus kisutch). 235 71

The tubular maximum for calcium reabsorption (TmCa) was evaluated in 52 patients with chronic active thoracic sarcoidosis. Hypercalcaemia was found in five patients (9.6%). The mean serum calcium value of 2.54 +/- 0.18 mmol.l-1 in patients with sarcoidosis was significantly higher than that obtained in the control group (2.42 +/- 0.11 mmol.l-1). The mean TmCa in patients with sarcoidosis (2.11 +/- 0.26 mmol.l-1 glomerular filtrate (GF] was not statistically different from the mean TmCa for the group of healthy subjects (2.18 +/- 0.23 mmol.l-1 GF). Urinary sodium corrected TmCa in both groups of patients was affected in a similar way. Our study demonstrates for the first time that there is no increase in TmCa in patients with chronic active thoracic sarcoidosis. Hypercalcaemia is not a result of an increased TmCa.
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PMID:The tubular maximum for calcium reabsorption in patients with chronic active thoracic sarcoidosis. 236 38


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