Uv. Gopalaswamy et al., EFFECT OF PROPRANOLOL ON RAT-BRAIN SYNAPTOSOMAL NA-K+-ATPASE, MG2+-ATPASE AND CA2+-ATPASE(), Chemico-biological interactions, 103(1), 1997, pp. 51-58
The beta blocker drug propranolol (PPL) significantly inhibited Na+-K-ATPase, Mg2+-ATPase and Ca2+-ATPase activities in a concentration dep
endent manner in rat brain synaptosomes. The concentrations required f
or 50% inhibition (IC50) ih the activity of these enzymes were 1.5-1.8
mM. The double-reciprocal plot of ATP-stimulated Na+-K+-ATPase activi
ty in the presence of PPL showed apparent decrease in K-m and V-max an
d the inhibition was of an uncompetitive type with respect to ATP. The
nature of inhibition by PPL of Na+-activated Na+-K+-ATPase activity w
as of a mixed type showing an increase in K-m and decrease in V-max. P
otassium activation kinetics of Na+-K+-ATPase displayed uncompetitive
type of inhibition with PPL since K-m and V-max were decreased. Magnes
ium activation of Mg2+-ATPase showed decrease in V-max with no apparen
t change in K-m in the presence of PPL. The drug inhibited synaptosoma
l Ca2+-ATPase in an uncompetitive manner. The observed inhibition of s
ynaptosomal ATPases indicates possible alterations In the synaptic tra
nsmission by the beta blocker drug PPL. (C) 1997 Elsevier Science Irel
and Ltd.