양식 넙치, Paralichthys olivaceus를 실험어로 하여 동물 성장인자중의 하나인 insulin-like growth factor-I (IGF-I)의 함량을 검토하였다. 넙치의 혈액중에 존재하는 IGF-I의 양은 47ng/㎖이고, 절식을 할 경우 식이를 섭취한 것에 비해 약 15% 감소하였으며, 운동에 의해서는 약 13%의 감소를 보였다. 혈액중 IGF-I의 농도는 어체의 크기에 따라서도 영향이 있음을 알수 있었다.

Insulin-like growth factor-I (IGF-I) is a mitogenic peptide with molecular mass of 7kDa. It is produced mainly in the liver and has important functions in the regulation of development and somatic growth. Recently, several investigations were undertaken to examine the biological actions and structures of IGF-I in fish. In this study, the serum levels of IGF-I were estimated from flounder, Parlichthys olivaceus, before, during and after fasting, and the levels were accounted for 47 ng/㎖, 40 ng/㎖ and 45 ng/㎖, respectively. These results suggest that food deprivation primarily reduces IGF-I level in the blood.