[Sensitivity of brain Na, K-ATPase to acetylcholine following heat treatment of membrane preparations].

Microsomal preparations of Na, K-ATPase, isolated from dog and bovine brains, were completely insensitive to acetylcholine (10(-6)-10(-2) M) under standard experimental conditions. At the same time, heat pretreatment of membranes induced alterations of the enzymatic activity in presence of low concentrations (10(-6)-10(-5) M) of the neurotransmitter. Acetylcholine stimulated the Na, K-ATPase activity after storage of the preparations at 22 degrees within 30 or 60 min inhibited the activity at 37 degrees. Addition of the transmitter during the preincubation increased its effect. The maximal values of Na, K-ATPase activation and inhibition constituted 30% and 24%, respectively. D-tubocurarine (10(-6)-10(-5) M) and atropine (10(-4) M) did not eliminate and eserine (10(-4) M) did not alter the induced effect of acetylcholine. The effects of acetylcholine were changed to the opposite ones within 70-90 days of storage of the preparations. The phenomenon might be simulated by "ageing" of microsomes at 37 degrees within 3-6 hrs.