Different properties of two brain extracts separated in Sephadex G-50 that modify synaptosomal ATPase activities.
We have previously reported that Na+,K+-ATPase of nerve ending membranes is stimulated by catecholamines only in the presence of a brain soluble fraction. The filtration of this soluble fraction through Sephadex G-50 permitted the separation of two extracts of maximal UV absorbance (peaks I and II) which showed different effects on ATPases. Peak I stimulated both Na+, K+-ATPase and Mg2+-ATPase activities and peak II inhibited Na+, K+-ATPase activity. We have now studied the activity of ATPases in the presence of the whole eluate obtained from the Sephadex G-50 column. It was observed that maximal effects on ATPases were obtained with peaks I and II. Peak I and peak II fractions were unable to modify the activity of acetylcholinesterase or 5'-nucleotidase present in the synaptosomal membranes. The stimulatory effect of peak I on ATPases was concentration dependent (up to 1:100), it was stable at different pHs and it was reverted by catecholamines. The inhibitory effect of peak II on Na+,K+-ATPase was concentration dependent (up to 1:50,000), it was stable only at acid pH, and it was partially reverted by catecholamines. These findings indicate that the factors responsible for the effects of peaks I and II have different properties and that their actions on ATPases show enzyme specificity.
Rodríguez de Lores Arnaiz
G
G
Instituto de Biología Celular, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Antonelli de Gómez de Lima
M
M
Girardi
E
E
D000818:Animals; D001923:Brain Chemistry; D002395:Catecholamines / Q000494:pharmacology; D002540:Cerebral Cortex / Q000032:analysis / Q000378:metabolism; D002850:Chromatography, Gel; D003911:Dextrans; D005260:Female; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology*; D014020:Tissue Extracts / Q000302:isolation & purification / Q000494:pharmacology*
D002395:Catecholamines; D003911:Dextrans; D014020:Tissue Extracts; C025614:sephadex; D000254:Sodium-Potassium-Exchanging ATPase