Estrogen and phytoestrogens: Effect on eNOS expression and in vitro vasodilation in cerebral arteries in ovariectomized Watanabe heritable hyperlipidemic rabbits.
OBJECTIVE
To evaluate the effect of estrogen replacement therapy or soy isoflavones supplement on endothelium-dependent relaxation in vitro and gene expression of endothelial nitric oxide synthase (eNOS) in cerebral arteries in a rabbit model of human hypercholesterolemia.


METHODS
Thirty-six female ovariectomized Watanabe heritable hyperlipidemic (WHHL) rabbits were randomised to treatment with 17beta-estradiol (17beta-E(2)), SoyLife 150 or control for 16 weeks. Ring segments of basilar artery (BA) and posterior cerebral artery (PCA) were mounted in myographs for isometric tension recordings. Concentration response curves to carbamylcholine chloride, sodium nitroprusside (SNP) and l-NAME were evaluated after precontraction with potassium. Total RNA was extracted, reverse transcribed and eNOS quantitated by real-time polymerase chain reaction (real-time PCR).


RESULTS
Plasma cholesterol was significantly higher at termination in the SoyLife group (P<0.0001), whereas low-density lipoprotein (LDL) cholesterol was comparable in all treatment groups. Neither treatment influenced the endothelium-dependent responses to carbamylcholine chloride or l-NAME or the endothelium-independent response to SNP in any of the arteries. Correspondingly, eNOS mRNA was similarly expressed in all treatment groups in both arteries.


CONCLUSIONS
Improvement of cerebral endothelial function by estrogen or soy isoflavones in ovariectomized WHHL rabbits is not supported by the present data. The findings may be unique to the WHHL rabbit in which the hypocholesterolemic effect of estrogens mediated by upregulation of liver LDL receptors is excluded.
Lund
Claus O
CO
Department of Obstetrics and Gynaecology, Hvidovre University Hospital, DK-2650 Hvidovre, Denmark. col@dadlnet.dk
Mortensen
Alicja
A
Nilas
Lisbeth
L
Breinholt
Vibeke M
VM
Larsen
Jens-Jørgen
JJ
Ottesen
Bent
B
D000818:Animals; D001488:Basilar Artery / Q000187:drug effects*; D008078:Cholesterol, LDL / Q000097:blood; D004195:Disease Models, Animal; D004730:Endothelium, Vascular; D004958:Estradiol / Q000097:blood / Q000494:pharmacology*; D015914:Estrogen Replacement Therapy; D005260:Female; D006949:Hyperlipidemias; D007529:Isoflavones / Q000097:blood; D052250:Nitric Oxide Synthase Type III / Q000187:drug effects* / Q000378:metabolism; D010052:Ovariectomy; D048789:Phytoestrogens / Q000494:pharmacology*; D020769:Posterior Cerebral Artery / Q000187:drug effects*; D011817:Rabbits; D011897:Random Allocation; D015854:Up-Regulation; D014664:Vasodilation / Q000187:drug effects*
D008078:Cholesterol, LDL; D007529:Isoflavones; D048789:Phytoestrogens; D004958:Estradiol; D052250:Nitric Oxide Synthase Type III