The female reproductive system is very sensitive to different harmful environmental factors. A great danger is hidden in an increased use of food additives like monosodium glutamate (MSG). Numerous studies have shown that application of high doses of MSG to different kinds of animals during the neonatal period may cause lesions of neural structures and the retina. Later in adulthood animals exhibit a series of neuroendocrine disorders: a stunted growth, obesity and infertility. The mechanism of MSG action is not well explained yet. We hypothesized that high concentration of MSG could alter permeability of neural membrane for calcium. We studied whether pretreatment with diltiazem prevented the effects of MSG on ovaries in rats. Female rat pups were treated with: 0.9% NaCl, MSG, diltiazem or diltiazem with MSG. MSG treatment resulted in a cystic degeneration of ovaries and irregular and prolonged estrus phase of estrus cycle. The other treated groups of rats had normal ovarian histology and estrus cycle. The pretreatment with diltiazem prevented development of morphological and functional disorders of ovaries. Our results suggest that calcium overloading play an important role in mechanisms of MSG toxicity.