High pressure antagonism of alcohol effects on the main phase-transition temperature of phospholipid membranes: biphasic response.
The combined effects of high pressure (up to 300 bar) and a homologous series of 1-alkanols (ethanol C2 to 1-tridecanol C13) were studied on the main phase-transition temperature of dipalmitoylphosphatidylcholine (DPPC) vesicle membranes. It is known that short-chain alkanols depress and long-chain alkanols elevate the main transition temperature. The crossover from depression to elevation occurs at the carbon-chain length about C10-C12 in DPPC vesicle membranes coinciding with the cutoff chain-length where anesthetic potency suddenly disappears. Alkanols shorter than C8 linearly decreased the transition temperature and high pressure antagonized the temperature depression. Alkanols longer than C10 showed biphasic dose-response curves. High pressure enhanced the biphasic response. In addition, alkanols longer than the cutoff length depressed the transition temperature under high pressure at the low concentration range. These non-anesthetic alkanols may manifest anesthetic potency under high pressure. At higher concentrations, the temperature elevatory effect was accentuated by pressure. This biphasic effect of long-chain alkanols is not related to the 'interdigitation' associated with short-chain alkanols. The increment of the transition temperature by pressure was 0.0242 K bar-1 in the absence of alkanols. The volume change of the transition was estimated to be 27.7 cm3 mol-1. This value stayed constant to the limit of the present study of 300 bar.
Tamura
K
K
Department of Anesthesia, University of Utah College of Medicine, Salt Lake City.
Kaminoh
Y
Y
Kamaya
H
H
Ueda
I
I
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D000438:Alcohols / Q000737:chemistry*; D000777:Anesthetics / Q000737:chemistry; D006874:Hydrostatic Pressure; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013696:Temperature
D000438:Alcohols; D000777:Anesthetics; D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine