[Effect of Chinoin-103 on K(+)-activated pNPPase in the rat heart].

: Effect of a new beta receptor blocking agent, an aryl oxybutanolamine derivative, the Chinoin--103 on K(+)-activated pNPP-ase activity has been studied. Propranolol and practolol were used as reference substances. It has been established that Chinoin-103 in concentration of 10(-4) M significantly hindered total pNPP-ase activity. On the other hand base pNPP-ase activity did not significantly change on the effect of the highest investigable concentration. Study of enzyme kinetic parameters has shown that decrease of base pNPP-ase activity can be attributed to decrease of reaction rate (Vmax decreases) at the same time enzyme affinity to pNPP substrate significantly increases (Km decreases). Taking into consideration the structural similarity of propranolol and Chinoin--103 it is presumable that Chinoin--103 can interact with components of membrane like propanolol and impediment of pNPP-ase activity can be attributed to the interaction.