Calcium (Ca) and magnesium (Mg) content were determined in muscle of 27 patients with Duchenne muscular dystrophy, 36 with other neuromuscular diseases, and 22 whose muscle biopsy specimens were histochemically normal. Muscle Ca was significantly elevated in all diseases studied but was about 50% higher in Duchenne dystrophy patients (p less than 0.0001). Mg was decreased by 44% in Duchenne dystrophy, compared with less striking deficits in other diseases (p less than 0.005). In older, nonambulatory Duchenne dystrophy patients, Mg was significantly lower than in younger, ambulatory patients (p less than 0.001); muscle Ca was the same in both groups. On the basis of noncollagen nitrogen concentration, muscle MG depletion could not be attributed solely to reduced muscle mass. These findings strengthen arguments for a role of Ca in the pathogenesis of muscular dystrophy and may implicate Mg depletion as another pathogenetic factor.

ABSTRACT' Factor V, a plasma protein cofactor necessary for optimal conversion of prothrombin to thrombin, is also present in considerable concentration in blood platelets (9.9 units per 109 platelets). Subcellular fractionation by. two methods has localized factor V in the a granules of-unstimulated platelets. ADP and epinephrine cause release of4.6% and 6.4%, respectively, ofthe total factor V, a process completely inhibited by cyclooxygenase alkylation by aspirin. In contrast, collagen causes release of 25% of platelet factor V, a process only partially suppressed by aspirin. Secretion of factor V depends on the availability of metabolic energy, because antimycin A,. an inhibitor of aerobic metabolism, and 2-deoxyglucose, an inhibitor of anaerobic glycolysis, together almost totally inhibited the secretion of factor V induced by collagen. The data establish that factor V is not normally available on unstimulated platelets but can be secreted from a granules upon stimulation with physiological agents such as ADP, epinephrine, and collagen. Because factor V is known to serve as a receptor for factor Xa, the exposure of factor V on platelets consequent to release would accelerate the process of blood coagulation.One year after the discovery of factor V in plasma, Ware et al.(1) recognized that platelets also contain an accelerator of prothrombin conversion. Though this coagulant activity was more stable to heat inactivation and storage than was plasma factor V, it was generally assumed to be the plasma factor adsorbed to the platelet surface (2, 3). In 1975, Breederveld et aL (4), using gel filtration to isolate platelets from plasma, found minimal activity of factor V associated with platelets but were able to increase the V activity by freeze-thawing. 0sterud et aL (5) confirmed this observation and showed that platelets contain an activated form offactor V as well as a platelet activator ofplasma factor V. Kane et aL (6) have presented convincing evidence that factor Xa binds to the platelet membrane at a binding site that is identical to or requires the presence of factor V.Despite these important observations, several questions remain in evaluating the influence of platelet factor V on the hemostatic and possible thrombotic processes. What is the sub, cellular localization offactor V? Are prostaglandin synthesis and metabolic energy required for its release? Do collagen, ADP, and epinephrine release factor V as thrombin does? This study attempts to answer these questions. MATERIALS AND METHODSBovine serum albumin (fraction V), ADP, epinephrine, and bovine fibrinogen (fraction 1, type IV, 93% clottable) were supplied by Sigma. Human fibrinogen (grade L, 95%

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