P-glycoprotein functional activity in «soviet chinchilla» rabbits during pregnancy

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P-glycoprotein (Pgp, ABCB1-protein) is a membrane transporter protein that plays the key role in pharmacokinetics of drugs with a broad spectrum of action. Substrates of this transporter are some medical drugs (antibacterial, antiretroviral, hypotensive) that are prescribed to pregnant women for long-term intake, sometimes throughout the whole gestation period.
 Aim to study the activity of Pgp on the organism level in rabbits of Soviet Chinchilla breed in pregnancy.
 Materials and Methods. The study was performed on 21 Soviet Chinchilla female rabbits (3000-3500 g). The animals were divided into 3 series. The first series (n=6) included rabbits with 7 days of pregnancy; the second series (n=5) - animals with 14 days of pregnancy; the third series (n=10) - rabbits with 21 days of pregnancy. 7 Days before the study and in the indicated gestation periods, functional activity of Pgp was assessed by the pharmacokinetics of marker transporter substrate – fexofenadine, after its single oral introduction (67.5 mg/kg). Besides, serum concentrations of progesterone, estradiol, testosterone and prolactin were determined by radio immune method
 Results. In all the studied gestational periods, serum concentrations of estradiol, testosterone and prolactin did not significantly differ from those before pregnancy, but the level of progesterone in blood serum was significantly elevated above the norm. On the 7th day of pregnancy pharmacokinetic parameters of fexofenadine did not show any reliable changes as compared to the initial va-lues. On the 14th day of pregnancy a reliable increase in Cmax, AUC0-t, T1/2 of fexofenadine was noted as compared to the parameters before pregnancy, which indicates a decrease in Pgp functional activity on the organism level. On the 21st day of pregnancy Cmax of fexofenadine remained elevated. Other pharmacokinetic parameters of fexofenadine did not show reliable changes. Conclusion. Reduction in Pgp functional activity, determined by the pharmacokinetics of its marker substrate (fexofenadine), was noted in rabbits of Soviet Chinchilla breed on the 14th and 21st days of pregnancy with the underlying significant increase in progesterone level.