Effect of raloxifene on the ovarian circulation in women after menopause

Raloxifene prevents endothelial dysfunction in aging ovariectomized female rats

Lack of an appropriate animal model has delayed the better understanding of mechanisms related to higher cardiovascular risk in women after menopause. The aging female rat may share some menopausal changes observed in women. However, most studies have attempted to mimic menopause by ovariectomizing young (6-12 weeks old) animals without taking into accounts the influence of aging and of declining ovarian function. Therefore, the present study examined changes in vascular reactivity in the aging (15 months old) female rat after ovariectomy and the effects of chronic raloxifene therapy on vascular reactivity and eNOS protein expression. Aortic rings were prepared from the three experimental groups of rats: sham-operated control, ovariectomized and ovariectomized aging rats receiving daily oral administration of raloxifene for 3 months. Aortic rings were suspended in organ baths for the measurement of isometric tension. Rings with endothelium contracted significantly more to phenylephrine after inhibition of nitric oxide/cyclic GMP-signaling pathway by L-NAME or ODQ (as an index of basal nitric oxide release) in control and raloxifene-treated ovariectomized rats than in ovariectomized rats. This effect was abolished upon mechanical removal of the endothelium. Phenylephrine induced greater contractions only in rings with endothelium from ovariectomized rats as compared with control rats and raloxifene treatment normalized this response. In the presence of L-NAME or ODQ, phenylephrine-induced contraction was similar in rings from the three groups. Rings relaxed more to thapsigargin and acetylcholine in raloxifene-treated ovariectomized rats than in ovariectomized rats. There was no significant difference in aortic eNOS protein contents among the different groups. These results suggest that chronic oral administration of raloxifene to aging ovariectomized female rats augmented the bioavailability of endothelial nitric oxide in isolated aortic rings without altering eNOS protein levels.

[Impact of HRT on the arterial carotid vascular tree]

Hormone replacement therapy (HRT) and arterial impact, this is a controversial subject since it is a large field that needs weeding, a theme in which new questions are raised by the cross-results of various studies conducted, and in which doubt is perhaps one of, or even the only, certitude that all the various specialists agree on. In this controversial climate, we feel that three important points should be underlined: the American studies, however reliable they may be, have been conducted with conjugated estrogens and the generalisation to the results of other types of hormones such as those prescribed in Europe is perhaps a little hasty; other factors of risk should be taken into consideration in the eventual potentialisation of the risk induced by such treatment; the venous and arterial vascular risks are not based on the same physiopathological mechanisms. Hence the increased risk in one or the other network system should perhaps not be amalgamated either.