DETOXICATION ROLE OF THE PLACENTA:

EFFECT OF EFFLUX TRANSPORTERS AND BIOTRANSFORMATION ENZYMES

František ŠtaudKatedra farmakologie a toxikologie

Univerzita Karlova v PrazeFarmaceutická fakulta v Hradci Králové

Placenta

EFFLUXTRANSPORTERS

ENZYMES?

Efflux transporters and enzymesof the placenta

Several ABC transporters have been localized in placenta: MDR1, BCRP, MRPs

Protection of fetus against xenobiotics from mother.

Efflux transporters and enzymesof the placenta – expression of P-glycoprotein

Novotna M, et al. Reprod Tox, 2004

RT-PCR

Western blotting

Efflux transporters and enzymesof the placenta

Enzymes of phase one (CYP1,2,3 families)phase two (GST, UDP-glucuronosyltransferase, sulphotransferase, N-acetyl transferase).

Clinical significance??

Mainly metabolism of steroid hormones (11-HSD).

Efflux transporters and enzymesof the placenta – expression of 11-HSD2

Staud F, et al. Placenta, 2005

RT-PCR

Western blotting

Dual perfusion of the rat placenta

Conversion capacity

100*metaboliteparent

metabolite

M>F clearance

pma

ffvmf wC

QCCl

.

.

F>M clearance

p

ffm w

QERCl

.

Pla

cen

ta

PK analysis of efflux transporter activity (in placenta)

MaternalCirculation

FetalCirculation

Passive clearance (Clpd)

famamefflux CK

VCl

/

max

Capacity limited clearance (Clefflux)

effluxpdT ClClCl Total clearance (ClT)

mampdTmf CK

VClCl

max

M>F transport

fampdTfm CK

VClCl

max

F>M transport

ABC

F > M

M > F

Effect of P-gp on placental transport of Rhodamine 123

Pavek P, Staud F, et al. J Pharmacol Exp Ther, 2003

Transplacental transport of Rho123

0

0,1

0,2

0,3

0,4

0,5

M>F F>M

Cle

aran

ce (

ml/

min

)

Effect of BCRP on transplacental PK of cimetidine

8.7116.7Km

2.47 7.14Vmax

0.0420.042CLpd

inhibitorcontrolF>M 

0.028 0.77 Km

0.00057 0.013 Vmax

0.043 0.041CLpd

inhibitorcontrol M>F

M-F clearance

0,000

0,010

0,020

0,030

0,040

0,050

0,060

0,001 0,01 0,1 1 10 100 1000

Maternal cim etidine concentration (uM)

Cle

aran

ce (

ml/m

in/w

)

control

inhibitor

mampdTmf CK

VClCl

max

F-M clearance

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,001 0,01 0,1 1 10 100 1000

Fetal cimetidine concentration (uM )

CL

(m

l/m

in/w

)

control

inhibitor

fampdTfm CK

VClCl

max

~ 0.042 ml/min

Effect of BCRP on fetomaternal efflux of cimetidine

Cimetidine (100nM) present in both circulations – fetal perfusate recirculated

Active efflux of cimetidine from fetal compartment

80

85

90

95

100

0 5 10 15 20 25 30

Time (min)

Con

cent

ratio

n (%

of t

ime

0)

Cimetidine concentration dropped by 13% over 30 min

Effect of BCRP/Pgp on transplacental PK

ABC

11-hydroxysteroid dehydrogenase (11-HSD2) in placenta

• Regulates transport of maternal glucocorticoids – conversion to inactive 11-keto form

• cortisol cortison (human)

• corticosterone 11-dehydrocorticosterone (rat)

11-HSD2 saturability

(M>F corticosterone 3-200nM)

Staud F, Mazancova K, Miksik I, et al. Placenta, 2005

corticosterone

11-dehydrocorticosterone

Conversion of fetal corticosterone

Inhibition and saturation

Staud F, Mazancova K, Miksik I, et al. Placenta, 2005

Conclusions

Efflux transporters in the trophoblast can remove substrates from fetus to mother.

Similarly, some enzymes may metabolize molecules in the fetal circulation.

Transporters and enzymes play a key role in detoxication of the fetus.

Acknowledgements

Current PhD students:Mgr. Martina ČečkováMgr. Antonín LibraMgr. Lukáš ČervenýMgr. Zuzana VackováMgr. Leoš FuksaMgr. Lenka CygalováMgr. Lucie ŠvecováMgr. Eva BrčákováColleagues:RNDr. Jiří Pácha, DrScMUDr. Stanislav Mičuda, PhDPharmDr. Petr Pávek, PhDProf. MUDr. Zdeněk Fendrich, CSc

Financial support:GAUKFRVŠ

Technical assistance:A. KunováD. Součková