Persian sturgeon insulin-like growth factor I: molecular cloning and expression during various nutritional conditions.

The effects of different periods of starvation (1, 2, 3, and 4 weeks) and subsequent re-feeding (over a 4 week) on the compensatory growth performance and insulin-like growth factor I (IGF-I) mRNA expression in liver and white muscle were investigated in juvenile Persian sturgeon (Acipenser persicus). First, a fragment of 617 nucleotides coding for IGF-I was cloned from liver, which included an open reading frame of 486 nucleotides, encoding a 162 amino acid preproIGF-I. This is composed of a 45 aa for signal peptide, a 117 aa for the mature peptide comprising the B, C, A, and D domains, and a 47 aa for E domain. The mature Persian sturgeon IGF-I exhibits high sequence identities with other sturgeon species and teleost, ranging between 68 and 95 %. The pattern of IGF-I mRNA expression in the liver and white muscle was measured in response to different periods of starvation and subsequent re-feeding. Nutritional status influenced IGF-I mRNA expression pattern in both liver and muscle. IGF-I mRNA expression in the liver increased during starvation, before decreasing after re-feeding. Furthermore, white muscle IGF-I mRNA expression showed better responses to nutritional status and decreased following starvation and increased by re-feeding. However, changes in the expression of IGF-I mRNA were not significantly different between any of the treatments in both tissues. These data suggest that muscle and liver IGF-I mRNA expression do not have a regulatory role for somatic growth induced by compensatory growth in Persain sturgeon.