Transport of the new quinolone antibacterial agents of lomefloxacin and ofloxacin by rat erythrocytes, and its relation to the nicotinic acid transport system

J Pharmacobiodyn. 1991 Aug;14(8):475-81. doi: 10.1248/bpb1978.14.475.


Transport mechanism of quinolonecarboxylic acid derivatives (quinolones), lomefloxacin and ofloxacin, in rat erythrocytes was investigated. The uptake of lomefloxacin by erythrocytes was apparently nonsaturable over the concentration range of 0.1-1.0 mM at 27 degrees C and pH 7.4. In the case of ofloxacin, however, the erythrocytes took up ofloxacin in a concentration dependent manner at 20 degrees C and pH 7.4, with a maximum rate (Jmax) of 28.8 +/- 0.98 pmol/10(6) cells/s and a Michaelis constant (Kt) of 0.92 +/- 0.15 mM. An increase in the medium osmolarity caused a decrease in the [14C]lomefloxacin uptake, indicating that the drug is transported into the intracellular space of erythrocytes. The uptake of [14C]lomefloxacin by the erythrocytes was independent of pH but increased above pH 6.0, and, moreover, was dependent on temperature with an activation energy of 16.6 kcal/mol. The uptake of [14C]lomefloxacin was competitively inhibited by a water-soluble vitamin, nicotinic acid, with an inhibition constant (Ki) of 16.1 mM, but not inhibited by 10 mM of L-alanine, glucose, p-aminohippuric acid (PAH), N-methyl-nicotinamide (NMN) or tetraethylammonium chloride (TEA). These lines of evidence suggest that the transport system of lomefloxacin and ofloxacin in rat erythrocytes is common with that of a water-soluble vitamin, nicotinic acid, to which quinolones are structurally analogous.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Infective Agents / blood*
  • Anti-Infective Agents / pharmacokinetics
  • Biological Transport, Active / drug effects
  • Erythrocytes / metabolism*
  • Fluoroquinolones*
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Male
  • Niacin / metabolism*
  • Niacin / pharmacology
  • Ofloxacin / blood*
  • Ofloxacin / pharmacokinetics
  • Osmolar Concentration
  • Quinolones / blood*
  • Quinolones / pharmacokinetics
  • Rats
  • Rats, Inbred Strains
  • Temperature


  • Anti-Infective Agents
  • Fluoroquinolones
  • Quinolones
  • Niacin
  • Ofloxacin
  • lomefloxacin