RESUMO
In the vagina there are several microorganisms. Their survival is fundamental to have a physiological environment in the vagina (ecosystem). The same vaginal environment playg a fundamental role to guarantee tho survival of resident microorganisms. Several factors, like changes of temperature and oxygenation, can interfere on vaginal ecosystem, but the resident vaginal microorganisms are the main factors to stabilize the vaginal ecosystem. The Doderlein's lactobacillus is the predominant vaginal microorganism. It is capable of fermenting the glycogen deriving from the decline of the eutrophic vaginal mmucosa, to lactic acid with release of hydrogen ions. The final result of that metabolism is an acid pH with values between 4-4.5. Vaginal pH undergoes physiologically changes from birth to menopause, according to changes of ovarian steroids occurring during woman's life. Adequate levels of estrogens play a fundamental role in the trophism of vaginal mucosa. In fact, estrogens increase the cellular content of glycogen. Exogenous acbvities on vaginal pH can be exerted by several factors, such as sexual activily, oral contraceptives, systemic diseases, vaginal infections (candidosis, thrichomonias, vaginosis), systemic or local therapies. They incrcase vaginal pH by acting through different mechanisms. The increase of vaginal pH is detrimental for the survival of Doderlein's lactobacillus, but not for the pathogenetic microorganisms whose replication, on the contrary, is favored by the absence of contraction exerted by Doderlein's bacillus. It has been showed that local acidifying substances (lactic acid, lactobacillus and substances recently synthesized like alpha-aminovalerianic acid, policarbophil and carbopol 934) are useful in restoring the biological and chemical characteristics of the vaginal ecosystem.