Exogenous recombinant bovine growth hormone stimulates growth and hepatic IGF expression in shovelnose sturgeon Scaphirhynchus platorhynchus

Sturgeon are a unique fish for physiological research as they are long-lived, slow-growing, and late-maturing. Furthermore, sturgeon growth hormones appear to share greater structural and molecular similarity with mammalian somatotropins than teleostean somatotropins. In this study, changes in insulin-like growth factor (IGF)-I and IGF-II mRNA expression and corresponding whole-body growth and composition following 6 weeks of bi-weekly recombinant bovine growth hormone (rbGH) administration in shovelnose sturgeon Scaphirhynchus platorhynchus were evaluated. Fish were injected intraperitoneally with 240 μg rbGH/g body weight or a sesame oil sham. Hepatic IGF-I and IGF-II mRNA abundance was significantly higher (P ≤ 0.02) in rbGH-treated fish, as were length (P < 0.001) and weight gain (P < 0.001). In addition, proximate whole-body analysis demonstrated a significant (P < 0.05) increase in protein composition of rbGH-treated fish versus sham-treated fish. There were no significant differences in whole-body moisture, lipid, or ash between the two treatments. These results demonstrate functional roles for GH and IGFs in the promotion of lean growth within this ancient fish species and support the view that the functional effects of GH on hepatic IGF-I expression and somatic growth are conserved from chondostrean to teleostean fishes.