Effects of localized Pasteurella haemolytica infection on erythromycin-binding properties of bovine alpha-1-acid glycoprotein, albumin, serum, and tissue chamber fluids.
The in vitro erythromycin-binding properties of bovine alpha-1-acid glycoprotein (AAG) and albumin were studied by using equilibrium dialysis. In addition, the proportions of free erythromycin in bovine serum and tissue chamber fluid before and 4 days after inoculation of subcutaneous tissue chambers with Pasteurella haemolytica were measured. At a concentration of 5 micrograms/ml, erythromycin was moderately bound to AAG (39% +/- 4% free) and was only slightly bound to albumin (86% +/- 2% free). Scatchard analysis of the data describing binding to pure bovine AAG indicated that erythromycin was bound to a single high-affinity (6.45 x 10(4) M-1) site on the protein. At lower total concentrations of erythromycin, the free concentrations of the antibiotic were lower in serum samples collected after infection (49% +/- 3% at 5 micrograms of erythromycin per ml) than in those collected before inoculation (55% +/- 3% at 5 micrograms of erythromycin per ml). Inoculation had no effect on binding to macromolecules in chamber fluids. Inoculated tissue chambers served as a convenient model for studying the effect of infection on drug-macromolecule interactions in interstitial fluid.
Walker
J L
JL
Department of Physiological Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater 74078.
Clarke
C R
CR
Hague
C M
CM
Bourne
D W
DW
Lessley
B A
BA
D000818:Animals; D002417:Cattle; D004917:Erythromycin / Q000378:metabolism*; D016978:Mannheimia haemolytica; D009961:Orosomucoid / Q000378:metabolism*; D010326:Pasteurella Infections / Q000378:metabolism*; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*
D009961:Orosomucoid; D012709:Serum Albumin; D004917:Erythromycin