Reproducible and time-dependent modification of serum protein binding in Wistar Kyoto rats.
BACKGROUND
The theoretical basis of the influence of (alterations in) plasma protein binding on pharmacokinetics (PK) is well-established. In contrast, the impact of protein binding on pharmacodynamics has not been examined in a systematic manner. Here we present an experimental approach to modify serum protein levels and binding in the rat, in a robust, reproducible, and time-dependent manner.


METHODS
Male Wistar Kyoto rats were divided into three different groups. The control group (n=4) did not receive treatment. In the cannulation(-) group (n=6) the rats were instrumented with three permanent blood cannulas. The rats in the cannulation(+) group received in addition to the cannulation a subcutaneous injection of turpentine oil of 100 microl/100 g bodyweight. The effects were characterized in terms of 1) the time course of serum levels of albumin and alpha(1)-acid glycoprotein (AGP), and 2) the effect on the ex vivo serum protein binding of S(-)-propranolol.


RESULTS
In control rats the AGP serum concentration was stable at a value of 169+/-16 microg/ml. In the cannulation(-) group a maximum ten- to fifteen-fold increase in serum AGP concentration was observed at 48 h post surgery, followed by a gradual return back to baseline within 1 week. In the cannulation(+) group a similar concentration-time profile for AGP was found, but without a complete return to baseline within 1 week and with a much higher variability. Ex vivo, an increase in AGP serum concentration from 55 to 675 microg/ml resulted in a profound decrease in the free fraction of S(-)-propranolol from 14+/-0.6 to 1.9+/-0.3%.


CONCLUSIONS
In conclusion, through cannulation alone the serum protein levels and binding were modified in a robust, reproducible and time-dependent manner. Therefore this experimental approach is suitable for the investigation of the influence of protein binding on both pharmacokinetics and pharmacodynamics.
van Steeg
Tamara J
TJ
Leiden Amsterdam Center for Drug Research, Leiden University, Division of Pharmacology, Leiden, The Netherlands.
Krekels
Elke H J
EH
Danhof
Meindert
M
de Lange
Elizabeth C M
EC
D000319:Adrenergic beta-Antagonists / Q000493:pharmacokinetics*; D000704:Analysis of Variance; D000818:Animals; D002404:Catheterization; D008297:Male; D008954:Models, Biological; D009961:Orosomucoid / Q000378:metabolism*; D011433:Propranolol / Q000493:pharmacokinetics*; D011485:Protein Binding; D051381:Rats; D011921:Rats, Inbred WKY; D015203:Reproducibility of Results; D012709:Serum Albumin / Q000378:metabolism*; D013997:Time Factors; D014425:Turpentine / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D009961:Orosomucoid; D012709:Serum Albumin; D011433:Propranolol; D014425:Turpentine