Abstract
Insulin-like Growth Factors (IGFs) and IGF-binding protein act as intra-ovarian regulators that modulate the proliferation and differentiation of the granulosa and theca cells. Moreover, the IGF system is involved in metabolism by modulating the synthesis and degradation of glycogen and protein in animals. However the effect of the IGF system on egg productivity or body growth in KNOC has not been studied in depth. Therefore, this study was performed to investigate differences of serum IGFs and binding protein expressions between two groups showing high and low egg production or body weight and to elucidate the relationship of IGFs with egg productivity and body growth. KNOCs were divided into high and low groups depending on their egg productivity or body growth, and sera were collected every 10 wk from 20 till 60 wk. Serum IGF-I and -II concentration were measured by RIA using human and mouse antiserum and chicken standards. IGFBP was detected by Western ligand blotting. IGF-I concentrations were significantly greater in the high egg production group compared with those in the low egg production group (30 wk, p<0.01; 20 and 40 wk, p<0.05). Also, differences in IGF-II amounts between the two groups were detected at 60 wk (p<0.05). But IGFBPs in the low egg production group were more intense than that in the high egg production group through the egg laying period. The correlation between IGF-I concentration and number of egg production is significantly positive (20 wk, r=0.2729: p<0.05; 40 wk, r=0.3500: p<0.01), while IGF-II shows no correlation with egg productivity. In male KNOC, IGF-I and -II concentrations in the high body weight group are lower than that in the low body weight group. Body weight also shows a negative correlation with the serum IGF-II concentration in male chickens (20 wk, r=-0.5901: p<0.01). Consequently, we suggest that IGFs and binding protein are (in)directly involved in the egg productivity and body growth in KNOC. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 4 : 481-488)
Highlights
The Korean Native Ogol Chicken (KNOC) is a protected species by Korean government (Protected SpeciesAct No 265)
Seo et al (2001) reported the relationship of Insulin-like Growth Factors (IGFs)-I genotype to body weight and Insulin-like growth factor-I (IGF-I) concentration of KNOC and Kang et al (2001) studied the association of steroid hormones with economic traits of KNOC. These two reports indirectly indicated the possibility of improvement in egg productivity and body weight in KNOC using measurement of the endocrine factor expression
The correlation between serum IGF-II concentration and egg productivity was not detected during the other periods (Table 3B). These results indirectly suggest that serum IGF-I rather than IGFII is involved in the egg productivity of KNOC
Summary
The Korean Native Ogol Chicken (KNOC) is a protected species by Korean government Seo et al (2001) reported the relationship of IGF-I genotype to body weight and IGF-I concentration of KNOC and Kang et al (2001) studied the association of steroid hormones with economic traits of KNOC. Chicken IGF-I stimulates proliferation and steroidogenesis of granulosa and theca cells (Onagbesan and Peddie, 1995; Roberts and Gordon, 1995). IGF-II, a single-chain polypeptide of 67 amino acids, participates in processes occurring in the theca-interstitial androgenproducing compartment (Giudice, 1992) and the IGF-II variant would be a major determinant of follicular fate (Armstrong and Hogg, 1996) These interactions of IGFs and hormones regulate the hierarchical development of granulosa and theca cells. The membrane was incubated for 5 hrs at room temperature with TBS-0.1% Tween-20, 1% BSA, and 0.5 to 1.0×106
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