Na+-Ca2+ exchange in rat brain microsomal membranes pretreated with pronase and/or SDS.
The effects of pronase and/or SDS pretreatment on Na+-Ca2+ exchange were studied in rat brain microsomal membranes. Pronase in concentrations that liberated 11% of the membrane proteins stimulated the Na+-Ca2+ exchange. When about 24% of the proteins were split off, the results did not differ from those in control experiments. When 40% or more of the proteins were solubilized, Na+-Ca2+ exchange was abolished. Pronase pretreatment did not change the Km value for Ca2+, it increased Vmax only. The effect of pronase was partially blocked by Trasylol. Neuraminidase had no effect on Na+-Ca2+ exchange. SDS pretreatment of the membranes inhibited Na+-Ca2+ exchange: when 25% of membrane proteins were solubilized with SDS, the Na+-Ca2+ exchange was abolished while the same amount of proteins split off with pronase did not change the rate of Na+-Ca2+ exchange as related to membrane proteins. Ischaemia lasting for 2-4 h or complete hypoxia which should stimulate endogenous proteinases due to the rise of free intracellular calcium did not influence the Na+-Ca2+ exchange. A decrease in Na+-Ca2+ exchange rate was observed when proteins with molecular weight between 45,000 and 20,000 were split off from the membranes. It is assumed that the Na+-Ca2+ antiporter is a polypeptide from the group of proteins within the above molecular weights.
Ruscák
M
M
Orlický
J
J
Juhász
O
O
Zachar
J
J
D000818:Animals; D007611:Aprotinin / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism*; D009439:Neuraminidase / Q000378:metabolism; D011402:Pronase / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology
D008565:Membrane Proteins; D012967:Sodium Dodecyl Sulfate; D007611:Aprotinin; D012964:Sodium; D009439:Neuraminidase; D011402:Pronase; D002118:Calcium