The dependence of the lipid bilayer membrane: buffer partition coefficient of pentobarbitone on pH and lipid composition

Br J Pharmacol. 1977 Sep;61(1):57-63. doi: 10.1111/j.1476-5381.1977.tb09739.x.

Abstract

1 The membrane/buffer partition coefficient of [14C]-pentobarbitone has been determined as a function of the lipid composition of bilayer membranes. 2 A new technique based on ultrafiltration gave comparable results to conventional techniques but required less time for equilbration. 3 The membrane/buffer coefficient was independent of pentobarbitone concentration in the range studies. 4 The apparent partition coefficient varied with pH and was a linear function of the degree of dissociation of pentobarbition. 5 Both the charged and uncharged forms of pentobarbitone partitioned into the membrane, the latter to a much greater extent than the former. 6 At low pH the highest partition coefficient observed was in egg phosphatidylcholine bilayer membranes. 7 Incorporation of cholesterol or phosphatidic acid into phosphatidylcholine membranes greatly reduced the partition coefficient. 8 High pressures do not greatly change these partition coefficients.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Buffers
  • Chemistry, Pharmaceutical
  • Cholesterol
  • Hydrogen-Ion Concentration
  • Lipids*
  • Membranes, Artificial*
  • Pentobarbital*
  • Phosphatidylcholines
  • Potassium Chloride
  • Solubility

Substances

  • Buffers
  • Lipids
  • Membranes, Artificial
  • Phosphatidylcholines
  • Potassium Chloride
  • Cholesterol
  • Pentobarbital