Few effects of multi-generational dietary exposure to genistein or nonylphenol on sodium solution intake in male and female Sprague–Dawley rats

Previous work in our laboratory indicated that lifelong dietary exposure to estrogen-like endocrine disrupters increased sodium solution intake in adult male and female rats. Here, we sought to discern the critical periods necessary for this alteration as well as establish the effects of lower dietary concentrations of genistein and nonylphenol. Male and female Sprague–Dawley rats (F0) consumed phytoestrogen-free chow containing 0, 5, 100, or 500 ppm genistein (≈ 0.0, 0.4, 8.0, and 40.0 mg/kg/day) or 0, 25, 200, or 750 ppm nonylphenol (≈ 0.0, 2.0, 16.0, and 60.0 mg/kg/day). Rats were mated within treatment groups and offspring (F1) maintained on the same diets. Mating for the F1, F2, and F3 (genistein only) was within treatment groups. At postnatal day (PND) 21, the F3 generation began to consume unadulterated phytoestrogen-free chow such that genistein exposure occurred only in utero and preweaning. The F4 generation was never directly exposed to genistein. On PNDs 65–68, intake of regular water and a 3.0% sodium chloride solution was measured for F1–F4 generations (genistein portion) or F1–F2 (nonylphenol portion). Although body weights were decreased by the highest dietary concentrations of genistein and nonylphenol, there were only minimal effects of exposure on sodium solution intake. As expected, intake was highest in female rats. With previous data, these results indicate that the dietary concentrations necessary to increase adult sodium solution intake in rats are greater than 500 ppm genistein and 750 ppm nonylphenol and such effects do not appear to increase across generations.