Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0020438 (hypercalciuria)
 2,502 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Squamous carcinomas are the most common cause of humoral hypercalcemia of malignancy (HHM) in humans. To develop an animal model of this syndrome, CD-1 female mice were painted with dimethylbenzanthracene, which produced cutaneous squamous carcinomas in the majority of those painted. Greater than 90% of tumor-bearing mice developed a syndrome of hypercalcemia, hypophosphatemia, hypercalciuria, elevated plasma 1,25-dihydroxyvitamin D, normal immunoreactive PTH, elevated urinary cAMP, and accelerated bone resorption compared to control mice. Tumor excision reversed the hypercalcemia and hypophosphatemia, and autopsies revealed no evidence of skeletal or other metastases. Dietary calcium restriction did not affect the hypercalcemia in tumor-bearing mice. Extracts of tumor tissue contained potent bioactivity paralleling that of bovine (b) PTH in a PTH-sensitive canine renal cortical adenylate cyclase assay. The activity was trypsin sensitive and partially inhibitable by Nle, Tyr bPTH amide. The activity coeluted with chymotrypsinogen (mol wt, 25,700) on Sephacryl S-200 chromatography, well ahead of bPTH. This is the first description of an animal squamous carcinoma that produces HHM. With the exception of elevated plasma 1,25-dihydroxyvitamin D levels, the syndrome precisely mimics that seen in human HHM. The presence of a biologically active protein larger than PTH in tumor extracts, similar to that extracted from human tumors, suggests a common mode of pathogenesis. This model should be useful in further studying the pathophysiology of HHM.
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PMID:Squamous carcinoma model of humoral hypercalcemia of malignancy. 649 73

The neonatal Bartter syndrome (NBS) is associated with a complex disorder of mineral metabolism in children, including hypercalciuria, nephrocalcinosis, and diminished bone mineral density. Although cyclooxygenase inhibition usually brings about improvement in these findings, there is a variable component which is resistant to such therapy in many children. The factor mediating this disorder has not been identified. Blood and urine from 12 children with NBS were examined. When compared with samples from normal children and adults, all (NBS) sera reduced bone calcium uptake in a bone disc bioassay. This effect persisted in the presence of parathyroid hormone (PTH) antibody and PTH receptor blockade, indicating that neither PTH nor PTH related peptide was responsible. It was eliminated by indomethacin, suggesting that prostanoid generation was essential. Protamine was also inhibitory, as was the addition of ecteola, an anion binder. Activity could be recovered from ecteola by elution with hypertonic buffer. Urine samples from children with NBS had the same calcitropic effect. The agent was removed by ecteola and recovered by hypertonic elution. Activity was eliminated by protamine and by heparinase, but not by trypsin digestion. Size exclusion centrifugation showed that the activity was associated with a material between 10 and 30 kilodaltons. Finally, urine ecteola eluates from NBS patients raised serum concentrations of calcium after intraperitoneal injection in rats. These data suggest that children with NBS have a calcitropic substance in their serum and urine which is not found in normal individuals. The substance is heparin like, and mediates its effects through prostanoid production. These studies provide additional evidence against a direct renal cause of the urinary calcium disturbance characteristic of the disorder.
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PMID:Humoral factor in children with neonatal Bartter syndrome reduces bone calcium uptake in vitro. 968 54

Vitamin D-elicited hypercalcemia/hypercalciuria is associated with polyuria in humans and in animal models. In rats, dihydrotachysterol (DHT) induces AQP2 water channel downregulation despite unaltered AQP2 mRNA expression and thus we investigated the mechanism of AQP2 degradation. Incubation of AQP2-containing inner medullary collecting duct (IMCD) endosomes with Ca(2+) or calpain elicited AQP2 proteolysis, an effect abolished by leupeptin. This endogenous, Ca(2+)-sensitive protease activity exhibited a different proteolytic digest pattern from trypsin, which also degraded AQP2 in vitro. IMCDs contain abundant micro-calpain protein and functional calpain proteolytic activity as demonstrated by immunohistochemistry, immunoblotting, and gel zymography. Furthermore, by small particle flow cytometry we demonstrated that micro-calpain colocalizes with apical IMCD endosomes. DHT does not appear to elicit general proteolysis, however, in addition to AQP2 degradation, DHT treatment also diminished micro-calpain and calpastatin expression although whether these changes contributed to the AQP2 instability remains unclear. Together, these data show for the first time that AQP2 is a substrate for calpain-mediated proteolysis and that furthermore, micro-calpain, like AQP2, is both highly expressed in renal inner medulla and localized to apical IMCD endosomes.
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PMID:Calpain-mediated AQP2 proteolysis in inner medullary collecting duct. 1264 65