Increased erythrocyte content of Ca2+ in patients with Tarui's disease.

Abstract

OBJECTIVES: To establish by flow cytometry and fluorophores an increased calcium ion load in erythrocytes of four patients with Tarui's disease. DESIGN: Calcium ion levels were determined in erythrocytes of patients and controls under normal and energy-deprived conditions. Adenylates were measured to assess energy status of incubated erythrocytes. SETTING: The experiments were carried out at the Department of Clinical Chemistry of the University Hospital of Uppsala, Sweden. SUBJECTS: Four family members with Tarui's disease participated in the study. The proband (patient 1) was a 39-year-old male; patients (male, aged 46 years) 2 and 3 (female, 30 years) were his two siblings. Patient 4 (male, 16 years) was the son of patient 2. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Calcium ion homeostasis was measured under basic conditions and under energy-deprived conditions and related to cellular adenylate content. RESULTS: All patients showed enhanced erythrocyte calcium ion loading compared to controls under energy-deprived conditions. Under normal conditions, however, three out of the four patients showed an increased erythrocyte calcium ion level compared to controls. CONCLUSIONS: We conclude that erythrocytes from patients with Tarui's disease have an increased Ca2+ permeability, initiating compensatory mechanisms involving increased Ca2+ pump activity and increased glycolytic flux, which are not always sufficient to keep erythrocyte calcium ion concentration within physiological range.