Studies on the chemical modification of monensin. II. Measurement of sodium ion permeability of monensylamino acids using sodium-23 nuclear magnetic resonance spectroscopy.
A technique to assay Na+ ions in cells is presented. Intracellular and extracellular Na+ ions in a suspension of guinea pig erythrocytes were conveniently determined by using sodium-23 nuclear magnetic resonance (23Na-NMR), in combination with two anionic shift reagents: Dy(TTHA)3- and Dy(PPPi)2(7-). Monensin (1), monensylalanine (2b), monensylserine (2c), and monensylphenylalanine (2d) induced large increases of intracellular Na+ ion concentration ([Nain]), while monensylglycine (2a), monensyltyrosine (2e), monensylaspartic acid (2f), and monensylglutamic acid (2g) showed slight increases. The values of initial increasing rate (Vi) of 2a-g were much smaller than that of 1. This fact was probably due to the lower lipophilicity of 2a-g than 1, because a good correlation was observed between Vi and Rm50 values of 1 and 2a-g. This lower lipophilicity is a consequence of conformational differences between 1 and 2a-g.
Nakamura
A
A
Nagai
S
S
Ueda
T
T
Sakakibara
J
J
Hotta
Y
Y
Takeya
K
K
D000596:Amino Acids; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008985:Monensin / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D010539:Permeability; D012964:Sodium / Q000378:metabolism*; D012979:Sodium Radioisotopes
D000596:Amino Acids; D012979:Sodium Radioisotopes; D008985:Monensin; D012964:Sodium