| Administration of estradiol to barrows has been demonstrated to cause an increase in serum and anterior pituitary (AP) concentrations of IGF-I and relative amounts of serum and AP IGFBP. Gilts have also been found to have an increase in serum and AP concentrations of IGF-I and relative amounts of serum and AP IGFBP with age, coincidently with an increase in serum estradiol concentrations. However, the effects of other estrogenic compounds on the porcine IGF system remain to be determined. Genistein, an isoflavone found in soybeans, has recently been shown to have estrogenic effects in pigs. Therefore, two experiments were conducted to determine if (1) intramuscular administration of genistein increased serum and AP concentrations of IGFI and relative amounts of serum and AP IGFBP in barrows and if (2) oral administration of genistein increased serum and AP concentrations of IGF-I and relative amounts of AP IGFBP in gilts. In experiment 1, twenty barrows of similar age (190 d) and weight (110 kg) were stratified by litter into one of four treatments: controls (C), estradiol (E), 200 mg genistein (200), and 400 mg genistein (400). The estradiol pigs were injected with 2 mg of estradiol-17beta i.m., while the 200 and 400 groups were injected with either 200 mg or 400 mg of 99% pure genistein i.m., respectively, for 15 d beginning on day 0. Blood was collected via jugular venipuncture on days 0, 3, 6, 9, 13, and 16. Blood and AP were collected at slaughter on day 16. Serum and AP concentrations of IGF-I were determined by RIA for both experiments 1 and 2. Relative amounts of serum and AP IGFBP were determined by Western ligand blot analysis for both experiments. Serum concentrations of IGF-I did not differ among groups (P>.05) throughout the 15 d and 21 d experiments. Anterior pituitary concentrations of IGF-I were greatest in E pigs (P<.05), while the 400 pigs had greater (P<.05) AP concentrations than C pigs. No difference was detected (P>.05) in AP concentrations of IGF-I between the 200 pigs and the C pigs. Relative amounts of serum IGFBP-2 and 46 and 41 kDa forms of IGFBP-3 did not differ (P>.05) among groups throughout experiment 1. Relative amounts of AP IGFBP-2 and -5 did not differ (P>.05) among groups throughout experiment 1 and between groups in experiment 2. In experiment 2, twenty-four crossbred gilts of similar age (150 d) and weight (77 kg) were stratified by litter one of two groups: control (C) and 400 mg of genistein (G). The C group received corn oil on top of their feed and the 400 mg group received a 99% pure form of genistein dissolved in corn oil on top of their feed for 20 days. Blood was collected via jugular venipuncture on days 1, 14, and 21. On day 21, anterior pituitary glands were collected, wrapped in foil, and frozen in liquid nitrogen then stored at -80°C. Reproductive tracts were collected for observations. Ovaries were examined for the presence of corpora lutea and corpora albicantia. Serum and AP concentrations of IGF-I were determined by RIA. Relative amounts of serum IGFBP were determined by Western ligand blot analysis. Serum concentrations of IGF-I did not differ between groups (P>.05) throughout the 20 d experiment. AP concentrations of IGF-I did not differ between groups (P>.05) throughout the 20 d experiment. Relative amounts of serum IGFBP-2 and -5 did not differ (P>.05) between groups throughout the experiment. These data provide evidence that genistein affects the AP IGF system in barrows. Even though the estrogenic potency of genistein is far less than that of estradiol, it is still able to trigger biological responses that are caused by physiological estrogens.Keywords: Genistein, Insulin-like Growth Factor, Binding Proteins, Barrows, Gilts, Estradiol... |
