The release of insulin–like growth factor - I by ovarian granulosa cells of pregnant sows after lead and mercury administration in vitro

Abstract

Lead (Pb) and mercury (Hg) are reproductive and developmental toxicants even at very low doses. The general objective of this study was to examine the secretory activity of porcine ovarian granulosa cells of pregnant sows after the lead and mercury in vitro administration. Ovarian granulosa cells were incubated with/without lead acetate, mercury chloride and follicle-stimulating hormone (FSH) for 18 hours. A maximal dose of Pb(CH3 COO)2 .3H2 O/ HgCl2 was 0.5 mg ml-1; group A - 0.25 mg.ml-1, group B - 0.083 mg.ml-1, group C - 0.063 mg.ml-1, group D - 0.046 mg.ml-1; in case of FSH: group E - 1.0 ng.ml-1, group G - 100 ng.ml-1. Group F received FSH (1.0 ng.ml-1), lead acetate (0.083 mg.ml-1) and mercury chloride (0.083 mg.ml-1); group H received FSH (100 ng.ml-1), lead acetate (0.063 mg.ml-1) and mercury chloride (0.063 mg.ml-1). Concentrations of IGF–I were determined in 25–100 µL incubation medium by RIA. In our study a significant release of IGF-I by ovarian granulosa cells from pregnant sows was revealed after lead administration at doses of 0.5 mg.ml-1 and 0.25 mg.ml-1. No significant changes at doses of 0.083 mg.ml-1, 0.063 mg.ml-1 and 0.046 mg.ml-1 were demonstrated. IGF-I was stimulated by the Hg addition at dose of 0.083 mg.ml-1. The concentrations 0.25 mg.ml-1, 0.063 mg.ml-1 and 0.046 mg.ml-1did not affect the release of IGF-I by granulosa cells. IGF-I release was not significantly stimulated by FSH (1 ng.ml-1), Pb (0.083 mg.ml-1) and Hg (0.083 mg.ml-1). Non-significant changes in the IGF-I output by granulosa cells after FSH (100 ng.ml-1), Pb (0.063 mg.ml-1) and Hg (0.063 mg.ml-1) administrations were noted. These observations suggest a possible involvement of heavy metals – Pb and Hg and pituitary hormone - FSH in a regulation of the growth factor IGF-I release by porcine ovarian granulosa cells of pregnant sows. Our results contribute to knowledge of mechanisms of lead and mercury effects on porcine ovarian granulosa cells of pregnant sows. However, uncontrolled growth of follicles by increased IGF-I level can be a possible risk factor of cancer.