β-adrenergic system in myotonic dystrophy

Abstract

Myotonic dystrophy (DM) is considered an inherited membrane disorder, but the basic defect is unknown. We studies plasma catecholamines as well as lymphocyte and muscle β-adrenergic receptor densities and functioning in 19 DM patients and 15 control subjects. Plasma adrenaline and noradrenaline concentrations were not significantly different between DM patients and controls. In isolated lymphocytes basal cAMP production was 157 ± 26 pmol/mg protein/10 min in DM patients and 91 ± 12 pmol/mg protein/10 min in controls (n.s.), whereas isoproterol-stimulated cAMP production was significantly higher in DM patients with (285 ± 42 pmol/mg protein) compared with control subjects (168 ± 21 pmol/mg protein, P < 0.05). Lymphocyte β-adrenoceptor densities were similar among DM patients (50 ± 3 fmol/mg protein) and controls (47 ± 5 fmol/mg protein). β-Adrenoceptor densities were also similar in muscle biopsy specimens (12.9 ± 1 in DM and 13.1 ± 13.1 ± fmol/mg protein in controls). The correlation between lymphocyte and skeletal muscle recert densities was r = 0.35in DM patients and r = 0.22 in controls. The results do not support the hypothesis of adrenergic dysfunction in DM despite its membrane involvement.