RESUMO
Arrhythmia was produced by the rapid intravenous injection of ouabain 200 micrograms/kg in anesthetized guinea-pigs. The incidence of ventricular fibrillation (V.F.) induced by the ouabain challenge was significantly decreased by the pretreatment with prostaglandin (PG) E1 5 micrograms/kg or propranolol 0.5 mg/kg, but not with prostacyclin (PGI2) 0.5 or 5 micrograms/kg. Also, a significant number of animals treated with PGE1 or propranolol, but not PGI2, showed recurrent reversion to sinus or ventricular rhythm from V.F. and survived more than 20 min after the ouabain challenge. On the other hand, almost all animals treated with PGI2 produced V.F., which converted to cardiac arrest within 20 min after the ouabain challenge. The finding shows that PGI2 has no protective action on V.F. induced by ouabain in anesthetized guinea-pigs. Involvement of norepinephrine released from sympathetic nerve terminals in ouabain-induced V.F. was assumed.
