PT  - JOURNAL ARTICLE
AU  - WARD E. HARRIS
AU  - WILLIAM L. STAHL
TI  - Effects of Cations and Propranolol on a Fluorescent Phospholipid Incorporated into Brain Synaptosome Membranes
DP  - 1976 Jan 01
TA  - Molecular Pharmacology
PG  - 115--126
VI  - 12
IP  - 1
4099  - http://molpharm.aspetjournals.org/content/12/1/115.short
4100  - http://molpharm.aspetjournals.org/content/12/1/115.full
SO  - Mol Pharmacol1976 Jan 01; 12
AB  - Dimethylaminonaphthalenesulfonyl-phosphatidylserine (DNS-PS), a fluorescent phospholipid, was incorporated into rat brain synaptosomes by a procedure utilizing the chaotropic agent sodium perchlorate. This procedure caused only minor changes in the electron microscopic appearance and protein composition of the membranes. Perchlorate treatment alone altered the activity of selected enzymes such as acetylcholinesterase and monoamine oxidase, but the insertion of DNS-PS within the membrane had only minor effects on the specific activities of synaptosomal enzymes. The fluorescence emission maximum of the membrane-bound DNS-PS was shifted to a slightly longer wavelength by addition of 100 mM NaCl or KCl, and the polarization of fluorescence decreased. The addition of 10 mM CaC12 shifted the emission maximum to a shorter wavelength, increased relative fluorescence 10-20%, and increased the polarization of fluorescence. Energy transfer from aromatic residues of membrane proteins to the DNS moiety was increased 11% by CaCl2, while MgCl2 had little effect, suggesting that Ca2+ may decrease the intermolecular distance between aromatic amino acids of membrane proteins and the fluorescent phospholipid. The beta adrenergic blocking agent propranolol reversed the changes caused by calcium and displaced at least a portion of the bound cation from the membrane. ACKNOWLEDGMENTS We thank Dr. Phil Smith for electron microscopic examinations of synaptosome preparations, and W. D. Northcroft of Ayerst Laboratories for the propranolol.