ISSN:
1432-1041
Keywords:
Gallopamil
;
protein binding
;
albumin
;
α1-acid glycoprotein
;
interspecies differences
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Medicine
Notes:
Summary There is little information about the factors which influence drug protein binding between species. We have therefore investigatived the role of pH on the binding of gallopamil, a calcium channel antagonist known to exhibit pH-sensitive binding, among four species, human, baboon, bovine, and canine. We used pure protein solutions of α1 acid glycoprotein (AAG) (60 mg·l−1), albumin (45 gm·l−1), and their combination and three values of pH, 7.0, 7.4, and 8.0. Gallopamil protein binding was determined over a concentration range of 2.0×10−7mol·l−1 to 2.1×10−3mol·l−1 using equilibrium dialysis. Gallopamil binding in all solutions was best described using a two binding site model in the combination solution and a one binding site model in the pure solutions. pH did not affect the number of identical binding sites. However, the influence of pH on gallopamil binding was species specific. Increasing the pH from 7.0 to 8.0 influenced binding affinity differently between species. There were directionally similar changes in unbound fraction at a gallopamil concentration of 2×10−7mol·l−1 as pH increased, although there were species differences in the degree of change. In protein solutions containing both AAG and albumin a reduction in pH from 7.4 to 7.0 resulted in species-specific increases in the unbound fraction. Increasing the pH from 7.4 to 8.0 again resulted in species-specific reductions in the unbound fraction of gallopamil. Similar changes were seen when pure AAG or albumin solutions were used, indicating species variance in both gallopamil protein binding and the effect of pH on binding.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00279978
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