The effect of growth hormone (GH) and testosterone injections on ovarian and liver insulin-like growth factor system was studied in Iranian native chickens. Two hundred hens were randomly assigned into four treatments. Each treatment consisted of five replicates. The number of hens in each replicate was 10. The daily ration contained 20% CP and 2800 cal ME/kg body weight (BW). Each hen received a daily allowance of 100 g of the ration and water was offered ad libitum. Treatments were: (1) injection (subcutaneous) of hGH (100 μg/kg BW), (2) injection of testosterone (500 μg/kg BW), (3) injection of hGH (100 μg/kg BW) + testosterone (500 μg/kg BW) and (4) injection of 100 μl distilled water (control group). Injections were made before puberty at 21st week of age before 5% oviposition of flock (flock puberty). The liver and ovary were removed 8 hours after each injection and immediately transferred stored at -80°C until used for determination of the IGF-I relative gene expression (Ovary extract was used for the determination of gene expression). Before each injection and again at 8 hours, blood samples were taken from the wing vein into EDTA-tubes from 15 hens in each experiment. The plasma concentration of estradiol, T3 and T4 were measured with ELISA. The data were analyzed using SAS 9.13 and the Real-time PCR softwares. The level of significance was set at P < 0.05. Estradiol concentration significantly decreased in testosterone and GH+testosterone groups. Plasma levels of T3 and T4 significantly increased in GH+testosterone hens. All hormonal injections resulted in a decreased expression of IGF-I gene in the liver. Hormonal treatments resulted in decreased expression of IGF-I in the ovarian extract as compared with the control hens. The expression of IGF-I gene in the liver significantly increased in testosterone-treated birds, compared with the control. The results indicated that injections of growth hormone and testosterone may influence the egg production by modifying the follicular growth and oviposition and so it can mediated via IGF-I gene.
