Effect of phospholipase A2 on temperature-induced high-affinity [3H]tryptamine binding sites in rat brain.
To investigate a link between membrane phospholipids and tryptamine binding molecules, we examined the effects of phospholipases A2 and D on the temperature-sensitive high-affinity [3H]tryptamine binding sites in rat brain. When the phospholipase A2-treated membranes were exposed to 1% bovine serum albumin (BSA) before assaying for [3H]tryptamine binding, a complete dose-dependent inhibition curve was observed. At a concentration of 0.03 U, the action of phospholipase A2 resulted in the splitting of phosphatidylserine (PS), choline phosphatides (PC) and ethanolamine phosphatides (PE) by about 32, 34 and 65%, respectively, and reduced [3H]ligand binding by about 32%. On the contrary, in the case of phospholipase D (500 U), PS and PC decreased by about 8% and 33% and PE by about 29% with no significant alteration in the binding capacity. Moreover, Scatchard analysis of the [3H]tryptamine binding showed that phospholipase A2 drastically increased only the KD value of the high affinity sites, and this was accompanied by a decrement of the Bmax values of both the high and low affinity binding sites. From these results, it is inferred that certain lipids (PS) may be a modulator for the function of the temperature-induced high-affinity [3H]tryptamine binding molecules.
Saito
M
M
Group of Neuropharmacology, Josai University, Saitama, Japan.
Serikyaku
S
S
Ishitani
R
R
D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008297:Male; D008563:Membrane Lipids / Q000502:physiology*; D010713:Phosphatidylcholines / Q000502:physiology; D010718:Phosphatidylserines / Q000502:physiology; D010739:Phospholipase D / Q000494:pharmacology; D010741:Phospholipases A / Q000494:pharmacology*; D054467:Phospholipases A2; D010743:Phospholipids / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013570:Synaptic Membranes / Q000378:metabolism*; D013696:Temperature; D014363:Tryptamines / Q000378:metabolism*
D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D010743:Phospholipids; D014363:Tryptamines; C030820:tryptamine; D010741:Phospholipases A; D054467:Phospholipases A2; D010739:Phospholipase D