INVOLVEMENT OF A PROTEASE IN TERT-BUTYLHYDROPEROXIDE-MEDIATED ACTIVATION OF CA2-MUSCLE( ATPASE IN MICROSOMES OF PULMONARY SMOOTH)

Microsomes isolated from bovine pulmonary artery smooth muscle tissue treated with the oxidant t-buOOH stimulated Ca2+ ATPase activity dose- dependently as also protease activity when tested with a synthetic sub strate N-benzoyl-DL-arginine p-nitroanilide. At 300 mu M t-buOOH optim ally stimulated these activities. Treatment of the microsomes with t-b uOOH stimulated ATP dependent Ca2+ uptake while Na+ dependent Ca2+ upt ake was inhibited by t-buOOH. Pretreatment of the microsomes with vita min E (1 mM) and aprotinin (1 mg/ml) prevented t-buOOH caused stimulat ion of protease activity and Ca2+ ATPase activity and also stimulation of ATP dependent Ca2+ uptake while t-buOOH caused inhibition of Na+ d ependent Ca2+ uptake was reversed by vitamin E and aprotinin. Treatmen t of the microsomes with trypsin (1 mu g/ml) stimulated Ca2+ ATPase an d ATP dependent Ca2+ uptake while Na+ dependent Ca2+ uptake was inhibi ted. Pretreatment of the microsomes with aprotinin prevented trypsin c aused stimulation of Ca2+ ATPase and ATP dependent Ca2+ uptake, while trypsin caused inhibition of Na+ dependent Ca2+ uptake was reversed by aprotinin.