Bone pyrophosphate in uremia and its association with extraosseous calcification.

The mean bone pyrophosphate was 0.360 +/- 0.15 mg/g in 8 controls and 1.22 +/- 1.39 mg/g bone in 27 uremic patients (P less than 0.0025). 13 of the 27 uremic patients had bone pyrophosphate levels greater than 2 SD above control values. The ash content of uremic bones with increased pyrophosphate levels (group II) was 56 +/- 9% as compared to 64 +/- 2% in control bones (P less than 0.01) and 60 +/- 7% in uremic bones having normal pyrophosphate levels (P less than 0.1) (group I). The magnesium content of bones in group II was 338 +/- 47 as compared to 211 +/- 13 (P less than 0.0005) in the controls and 294 +/- 73 mmol/kg ash (P less than 0.05) in group I. In group II, but not group I, there was a significant inverse correlation between duration of dialysis and percent bone ash (r = -0.59) (P less than 0.05). A definite relationship existed between elevated bone pyrophosphate levels and soft tissue calcification. In group II the mean pulmonary calcium content was 530 +/- 459 as compared to 32 +/- 26 mmol/kg/ash in group I (P less than 0.0025). All patients with a bone pyrophosphate level greater than 1.4 mg/g bone had extensive pulmonary calcification. It is concluded that the excess bone pyrophosphate present in some uremic patients is either deposited in the apatite crystal in the transphosphorylated form or else as the magnesium salt since the pyrophosphate is resistant to pyrophosphatase and surface adsorption of pyrophosphate is not altered by the increased bone pyrophosphate levels. The excess bone pyrophosphate could disturb bone calcification mechanisms in uremic patients. The association between increased bone pyrophosphate and soft tissue calcification suggests that the disordered pyrophosphate metabolism may be important in the pathogenesis of extraosseous calcification.

Extraosseous calcification. Evidence for abnormal pyrophosphate metabolism in uremia.

The inorganic constituents and crystalline features of extraosseous calcium-phosphate deposits obtained from dialyzed uremic and hypercalcemic patients were studied. Visceral calcification (heart, lung, and kidney) in hypercalcemic patients exhibited either an amorphous or apatitic X-ray diffraction pattern. Uremic visceral calcification consistently gave an amorphous diffraction pattern. Although the calcium content of uremic and hypercalcemic visceral deposits was similar, other inorganic constituents were different. The mean pyrophosphate was 11 +/- 11.8 and magnesium 4.91 +/- 3.86 mg/g in the uremic group as compared to 0.92 +/- 0.24 and 1.36 +/- 1.26 mg/g in the hypercalcemic group (P less than 0.025). After incineration hypercalcemic visceral deposits having an amorphous diffraction pattern were found to generate pyrophosphate supporting the presence of brushite in these deposits. The small amount of pyrophosphate in apatitic deposits from both uremic and hypercalcemic patients actually decreased after incineration and the pyrophosphate content of uremic visceral deposits was unchanged by incineration. It is concluded that in hypercalcemic patients the initial visceral deposit is brushite which is subsequently transformed to apatite. Arterial and tumoral calcium-phosphate deposits in uremic patients were also apatite. Uremic visceral calcium-phosphate deposits are an unique mineral high in magnesium with approximately 30% of the phosphorus present as pyrophosphate. The high pyrophosphate content of these deposits could alter their crystalline structure and prevent the transformation to apatite. The infrared features, high magnesium content of the deposit, and resistance of pyrophosphate in the deposit to hydrolysis by pyrophosphatase suggests that the pyrophosphate may be deposited as the magnesium salt.

Decreased insulin binding and degradation associated with depressed intracellular ATP content.

The effect of metabolic inhibitors, 2,4-dinitrophenol (DNP) and NaF, on insulin binding and degradation has been studied in cultured Buffalo rat liver (BRL) cells. In control studies, 1.8 fmol of 125I-insulin binds to 1.2 x 10(6) cells, possessing approximately 40,000 receptor sites per cell with binding affinity of 5.52 x 10(-8) M. When the cells were preincubated with increasing concentrations of either DNP or NaF, a dose- and time-dependent decrease in both insulin binding and degradation was observed. The total amount of 125I-insulin bound to BRL cells preincubated with metabolic inhibitors was reduced to 1.2 fmol per 1.2 x 10(6) cells. The point of 1/2 B max was achieved in the presence of 50 ng/ml of native insulin, 1.7 times that of the control level. The number of receptor sites was unaffected by either DNP or NaF, but an average affinity profile revealed a decrease in the affinity of the ATP-depleted cells for insulin (KD: 7.31 x 10(-8) M and 7.06 x 10(-8) M in DNP- and NaF-treated cells, respectively). The decrease in insulin binding and degradation following the exposure of the BRL cells to the metabolic inhibitors was associated with a 20% reduction in intracellular ATP and adenylate energy charge. DNP and NaF did not affect the equilibrium constant for the myokinase catalyzed reaction and the intracellular concentration of hypoxanthine was stable, confirming the integrity of the cells during the experiments. It is suggested that ATP levels must remain intact to maintain normal insulin receptor affinity. Furthermore, the rate of insulin degradation by ATP-depleted cells is slower than that of intact cells. It is conceivable that the depression of insulin degradation by partially ATP-depleted cells results from either diminished binding or decreased endocytosis and lysosomal activity, all of which appear to be energy dependent.

Distinction between the common symptoms of the phosphate-depletion syndrome and glucocorticoid-induced disease.

A phosphate depletion syndrome developed in a steroid-dependent asthmatic patient. Initially, the clinical picture was confused with steroid-associated myopathy rather than the phosphate depletion syndrome which has similar symptoms. The classic biochemical findings led to the correct diagnosis. Cessation of phosphate-binding antacids and phosphorus repletion rapidly corrected the biochemical findings and led to the patient's clinical improvement. Platelet phosphate metabolism was evaluated; it was found to correlate with the phosphorus-depleted state and clinical recovery with phosphate repletion. Attention is drawn to the clinical entity of phosphate depletion which may mimic steroid-induced side effects, both of which may occur in patients receiving steroids and antacids.

Management of pregnancy in osteogenesis imperfecta: new perspectives.

Osteogenesis imperfecta during pregnancy presents increased risk to mother and fetus. In addition to the well-known skeletal changes, other recently recognized metabolic abnormalities also may lead to maternal and fetal problems during labor and delivery. A discussion of risk factors and their managment is presented. The importance of considering the possibility of fetal osteogenesis imperfecta is stressed, and cesarean section is presented as the method of choice for delivery. Important genetic factors including the lack of correlation between the severity of involvement of parent and offspring and the use of pyrophosphate analyses are discussed. An illustrative case is presented.

Current concepts of malignant hyperthermia.

Malignant hyperthermia (MH) is a chemically induced, genetic myopathy characterized by metabolic and respiratory acidosis, arrhythmias, hyperpyrexia, and muscular rigidity usually occurring during or within 24 hours postanesthesia. It is initiated by some anesthetic drugs, muscle relaxants, and possibly by catecholamines produced by stress. The incidence of the disease is 1:15,000 in populations who have received a general anesthetic. A recently developed platelet bioassay test allows for rapid identification of the susceptible individual, while medication with dantrolene sodium can usually prevent or reverse the syndrome.

Calcium citrate for vulvar vestibulitis. A case report.

A woman had suffered from vulvar vestibulitis (vulvodynia) for four years. Pain from the disorder had disrupted her ability to function at work and home as well as sexually. An initial full range of treatments, including multiple operations, had produced no relief. Examination of the urine for evidence of excess oxalate, which has been shown to cause epithelial reactions similar to those found in vulvodynia, showed periodic hyperoxaluria and pH elevations related to the symptoms. Calcium citrate was given to modify the oxalate crystalluria. The symptoms were significantly reduced in three months, and the patient was pain free after one year. She was able to resume normal work, family, sexual and recreational activities. Withdrawal of the calcium citrate resulted in a return of the symptoms; reinstitution alleviated them. These findings suggest that further study of individualized metabolic factors that may underlie vulvodynia is warranted.

Biochemical abnormalities in workers exposed to molybdenum dust.

Exposure to molybdenum in dust was measured in a molybdenite roasting plant. This exposure was accompanied by large elevations of serum ceruloplasmin and smaller increases in mean serum uric acid levels in the workers. Absorption of molybdenum from the dust was demonstrated by increases in plasma and urinary molybdenum levels. It remains necessary to demonstrate whether such exposure results in long-term health effects.

Platelet model for halothane-induced effects on nucleotide metabolism applied to malignant hyperthermia.

A relatively non-invasive screening technique using venous blood analyzed by high performance liquid chromatography (HPLC) was developed to assess the effects of halothane on platelet nucleotide metabolism. Platelets were selected for study because of their contractile characteristics and many metabolic similarities to voluntary muscle. Platelets of 22 patients who previously had a documented clinical episode of malignant hyperthermia demonstrated a significant change in their nucleotide profile due to halothane exposure compared to normal subjects and 10 patients with musculo-skeletal and metabolic disorders. These results showed 100% correlation with the skeletal muscle contracture test for malignant hyperthermia (PHB). The platelet-halothane bioassay is highly reproducible and specific for detecting malignant hyperthermia with a significant degree of expression at the time of venipuncture. The assay deserves further study as an aid to the diagnosis of the degree of malignant hyperthermia susceptibility.

Calmodulin activity in corticosteroid-induced osteopenia.

A reproducible high-pressure liquid chromatography assay of calmodulin, a multifunctional calcium-dependent modulating protein, was developed for cartilage and bone by using cyclic nucleotide phosphodiesterase activity as the basis for standard curve determination. Calmodulin activity was then measured in rabbits that were made osteopenic by prednisolone injection in an effort to characterize in vivo cellular events. A significant rise in bone calmodulin levels was noted when this data was correlated with osteocyte and osteoblast content by quantitative histomorphometry. This suggests that calmodulin mediates steroid effects on the collagen matrix as well as on calcium homeostasis. Diminished calmodulin levels in weight-bearing cartilage of steroid-treated animals has as yet unresolved significance. Further characterization of calmodulin activity appears warranted in the study of osteopenic states at the subcellular level.

Elevated plasma adenine nucleotide levels in chronic renal failure and their possible significance.

Plasma ATP, ADP and AMP levels are increased in uremia. The elevation in plasma ATP level correlates with the serum creatinine in chronic renal failure patients not on dialysis. Successful renal transplantation is associated with the return of ATP, ADP and AMP levels to the normal range. Plasma ATP elevations may reflect sickness on the cellular level in uremia and measurement of plasma ATP may be a useful test to assess the need for dialysis. Plasma ATP elevations could also reflect underexcretion in the urine. Irrespective of the mechanism responsible for increased plasma ATP levels in uremia, an elevation of plasma ATP could have major physiological and metabolic consequences.

The effects of perfusion on an amputated extremity.

The amputated hindquarters of adult female rats were infused with solutions of lactated Ringer's, Collins hypertonic renal perfusate, and dextran-dextrose on a washout and continuous basis. The perfusate was analyzed for energy compounds and breakdown products and the muscle tissue examined histologically. Intermittent perfusion or injection under pressure led to marked edema in a 4-hour period and was abandoned in favor of a system that perfused the part at 120 to 150 cm H2O. The model perfused with Collins gained an average of 1.35 gm, that with lactated Ringer's 2.35 gm, and that with dextran-dextrose lost 2.35 gm. Pressure graphs of the various solutions indicated that the vascular bed reacts more physiologically to Collins solution and dextran-dextrose than to lactated Ringer's. Histologic sections of the muscle biopsies confirmed this. The release of ATP and hypoxanthine with lactated Ringer's suggests that it is the most damaging of the perfusates. These findings support the results of the pressure graphs and histologic studies. A potential for replantation of amputated limbs that contain muscle when the cold ischemia time may exceed 6 hours is suggested by the data presented.

Dantrolene sodium in the management of patients at risk from malignant hyperthermia.

Malignant hyperthermia is a dominantly inherited, usually subclinical, disease that occurs in individuals who have an underlying muscular disorder and connotes the gravest possible consequences. When it occurs, it is usually during the use of muscle relaxants in anesthesia and potent anesthetic agents such as halothane. Patients at risk must be identified through careful history and screening procedures; however, a patient susceptible to this condition may have had general anesthesia in the past without complications. A careful monitoring regimen must be established for the procedure and some means of cooling the patient must be ready in case pyrexia occurs. Dantrolene sodium is currently the preferred drug for prevention of the syndrome and may be valuable for its treatment.