A comparative study on the effect of insulin-like growth factor-I (IGFI) with DHP, hCG and aceton dried pituitary of Persian sturgeon (adsP) on in vitro germinal vesicle break down (GVBD) was examined in oocytes of the Persian sturgeon. Moreover, the effect of DHP and hCG in pretreated oocyte with IGF-I was examined. This study was carried out on two maturational stages of oocytes according to polarization index (PI<0.07 and PI>0.1). The oocytes used on two germinal vesicle positions, underwent GVBD in response to IGF-I (10, 100, 1000 ng/ml). The rate of GVBD was varied on each dose. In oocytes with PI<0.07, IGF-I (10, 100 ng/ml) was more potent than DHP (10 ng/ml) while in oocytes with PI>0.1, IGF-I (100, 1000 ng/ml) was more potent than DHP (10, 100ng/ml) on GVBD induction. IGF-I (10 ng/ml) in PI<0.07 and (100, 1000 ng/ml) in PI>0.1 induced more GVBD than hCG (10,100,1000 IU/ml). In two PI,s, adsP was more potent than IGF-I. Pretreatment of oocytes (PI<0.07 and PI>0.1) with IGF-I (100,1000 ng/ml) and then treatment with DHP (100 ng/ml) could increase GVBD as compare to oocytes that was not pretreated. Oocytes pretreated with IGF-I (1000 ng/ml) and then treated with hCG (100, 1000 IU/ml) underwent GVBD only in PI>0.1 (P<0.05). These results suggest, for the first time in sturgeon fish, that IGF-I is involved in the induction of GVBD of oocytes. IGF-I appears to act directly on oocyte as well as in conjunction with DHP or hCG, to induce GVBD.
