Fine structure of myonecrosis following adrenalin-induced cerebral vasospasm

Abstract

Frank necrosis of the media (myonecrosis) which could be confirmed by light microscopy was previously produced by the authors after the injection of adrenalin into the canine chiasmatic cistern. It is the purpose of this paper to report ultrastructural features of myonecrosis following adrenalin-induced cerebral vasospasm. The latter was induced in 10 dogs by a single subarachnoid injection of 0.2 mg/kg of adrenalin. Two dogs died of cerebral vasospasm 3 and 6 days respectively after the experiment, whereas eight other dogs were killed between 2 and 90 days. Microscopically, the circle of Willis showed coagulation necrosis and fibrosis of the media. The fine structure of myonecrosis was characterized by six dynamic changes of vacuolation, dissolution of myofilaments, focal cytoplasmic necrosis, fragmentation, coagulation necrosis and intercellular fibrosis. Despite a simple experimental procedure, the present models disclosed myonecrosis with a marked similarity to humans and contained all of the previously reported ultrastructural features of experimental myonecrosis. It is suggested that sustained contraction of smooth-muscle cells beyond their metabolic capability results in the mechanical destruction of myofilaments.