The inhibitory influence of toluene on mare ovarian granulosa cells can be prevented by fennel

•Toluene alone inhibited viability, proliferation, apoptosis, progesterone, prostaglandin F and IGF-I. However, it did not affect oxytocin release.•Moreover, Fennel, when given alone, inhibited viability, progesterone, and prostaglandin F release, as well as stimulating proliferation and oxytocin release.•In addition, Fennel did not affect apoptosis. When given in combination with toluene, fennel was able to suppress, and even invert, the effects of toluene on viability, proliferation, apoptosis, prostaglandin F, and IGF-I.•However, it did not alter its effect on progesterone release. Moreover, fennel induced the inhibitory effects of toluene on oxytocin output. Our studies could contribute to understanding the mechanisms of negative effects of environmental contaminants on female reproduction, as well as to prevention or treatment of this effect by using fennel. The influence of environmental contaminant toluene and of plant fennel (Foeniculum vulgare Mill.) on reproduction are reported, but the mechanisms of their action and the protective effect of fennel on contaminant influence remain to be elucidated. In this study, we hypothesized that toluene and fennel directly affects basic ovarian cell functions, and that fennel can be used as an appropriate natural protective agent against the potential adverse effects of toluene. This study aimed to examine the action of toluene (20 μg/mL) and fennel extract (0, 1, 10, 100 μg/mL), and assess their combination on viability, proliferation, apoptosis, and hormone release by cultured healthy mare ovarian granulosa cells. Viability, proliferation (percentage of PCNA-positive cells), apoptosis and release of progesterone, oxytocin and prostaglandin F were evaluated by using Trypan blue exclusion tests, immunocytochemistry and enzyme immunoassays, respectively. Toluene, when given alone, inhibited viability, proliferation, apoptosis, progesterone, prostaglandin F and IGF-I. However, it did not affect oxytocin release. Moreover, Fennel, when given alone, inhibited viability, progesterone, and prostaglandin F release, as well as stimulating proliferation and oxytocin release. In addition, Fennel did not affect apoptosis. When given in combination with toluene, fennel was able to suppress, and even invert, the effects of toluene on viability, proliferation, apoptosis, prostaglandin F, and IGF-I. However, it did not alter its effect on progesterone release. Moreover, fennel induced the inhibitory effect of toluene on oxy