pyrophosphate and Magnesium-Deficiency

Inorganic pyrophosphate (PPi) levels were estimated by radiometric assay in urine and in synovial fluid (SF) from asymptomatic, nonarthritic knees of patients with untreated metabolic disease and normal controls. SF PPi was significantly elevated in patients with hyperparathyroidism (mean +/- SEM 19 +/- 3 microM; n = 9), hemochromatosis (23 +/- 5 microM; n = 6), and hypomagnesemia (27 +/- 0.1 microM; n = 2) compared with normal subjects (10 +/- 0.5 microM, n = 50), and was low in patients with hypothyroidism (4.2 +/- 2.3 microM; n = 11) (P less than 0.05 all comparisons). Urinary PPi was elevated only in those with hypophosphatasia. Local elevation of ionic PPi may be relevant to the mechanism of crystal formation in metabolic diseases predisposing to calcium pyrophosphate dihydrate (CPPD) crystal deposition. The finding of low SF PPi levels in patients with hypothyroidism further questions the association between this condition and CPPD.

Topics: Adult; Aged; Aged, 80 and over; Calcium Pyrophosphate; Creatinine; Crystallization; Diphosphates; Endocrine System Diseases; Female; Hemochromatosis; Humans; Hyperparathyroidism; Hypophosphatasia; Hypothyroidism; Magnesium Deficiency; Male; Metabolic Diseases; Middle Aged; Synovial Fluid

The clearance rate of isotopically labeled synthetic triclinic calcium pyrophosphate dihydrate (CPPD) crystals injection into rabbit joints was estimated by serial counting. Kinetic analysis using a four compartment model showed that half of the injected dose was cleared from 4 rabbit knee joints in 19.1 +/- 0.42 (SEM) days. Profound hypomagnesemia, produced in 2 rabbits with a low magnesium diet, did not affect the rate of crystal clearance detectably. Lavage of joints with solutions known to promote CPPD crystal solubility failed to remove detectable radioactivity. The previous finding of CPPD crystals in synovial phagocytes by electron microscopy, together with the finding of nuclide activity in the synovium and the failure to remove such activity by joint lavage, suggests that endocytosis by synovial cells is an important, effective mechanism controlling the synovial fluid concentration of crystals in patients with CPPD crystal deposition disease.

Topics: Animals; Calcium Pyrophosphate; Calcium Radioisotopes; Diphosphates; Edetic Acid; Isotope Labeling; Joints; Knee Joint; Macrophages; Magnesium; Magnesium Deficiency; Methods; Rabbits; Strontium Radioisotopes; Synovial Fluid; Synovial Membrane; Therapeutic Irrigation

In two cases of Bartter's syndrome with hypomagnesaemia the authors report radiological findings typical of chondrocalcinosis associated with joint symptoms corresponding to this condition. In Bartter's syndrome there is, in addition to hypokalaemic alkalosis, often concomitant magnesium depletion which has marked repercussions with respect to both physiopathology and symptomatology. In particular, hypomagnesaemia could well be important in the pathogenesis of chondrocalcinosis through two simultaneous mechanisms: by reducing the activity of pyrophosphatases and by facilitating the crystallisation of pyrophosphates. These mechanisms could explain the association of Bartter's syndrome and chondrocalcinosis, which is described here for the first time.

Topics: Adult; Alkalosis; Bartter Syndrome; Chondrocalcinosis; Crystallization; Diphosphates; Female; Humans; Hyperaldosteronism; Hypokalemia; Magnesium Deficiency; Male; Potassium; Pyrophosphatases

Topics: Animals; Diet; Diphosphates; Liver; Magnesium; Magnesium Deficiency; Rats; Thiamine; Thiamine Deficiency; Transferases