EXPRESSION OF THE GROWTH-HORMONE GENE DURING EMBRYONIC AND POSTHATCH DEVELOPMENT OF THE CHICKEN

Growth hormone (GH) gene expression was investigated in both sexes of two strains - a laying- and a broiler-type-of chicken during embryonic (beginning from day 4 of incubation, E4) and posthatch (up to day 56, D56) development using the in situ hybridization technique and Northe rn blot analysis. GH mRNA was first detected within the primordial pit uitary at E7. After E14 consistent and strong were observed in all spe cimens with a progressive increase between E14 and D7. Obvious differe nces between broiler and layer strains were observed during embryonal life, with higher levels of GH gene expression in broiler-type compare d to laying-type chicken. During posthatch development sex differences were detectable in all age groups of broilers, with higher levels in males throughout. While signal intensities decreased remarkably after D28 in the broiler strain, the laying-type animals seemed to express G H mRNA more continuously, reaching the highest amount of GH transcript . at D56 which was the oldest stage investigated in this study.