| This work represents the first characterization of an IGFBP in a chondrichthyean fish. The round stingray possesses 2 IGFBPs in the blood circulation: a ∼45 kDa IGFBP and a ∼24 kDa IGFBP. RT-PCR produced an 1140 bp cDNA, which includes 522 bp of coding sequence that encodes a protein of 174 amino acids. The C-terminus contains 6 highly conserved cysteine residues, as well as a putative heparin binding domain. Genetic distance analysis of this IGFBP indicates that the stingray IGFBP-3 is most similar to mammalian IGFBP-3, as compared with teleost IGFBP-3. Semi-quantitative RT-PCR analysis showed the highest IGFBP-3 mRNA levels in the liver, kidney, spiral valve, uterus, skin, eye and gill, and the lowest in ovary, testis, and seminiferous tubules. The acquisition of this elasmobranch IGFBP-3 cDNA sequence has begun to provide for a better understanding of the growth endocrine axis in a poorly understood, yet important group of fishes. |
