Neuroendocrine Regulation of Growth Hormone Secretion and Body Growth in Carp: A Review

Growth hormone (GH) secretion in carp is stimulated by a number of neuropeptides (e.g., GH-releasing factor, gonadotropin-releasing hormone, thyrotropin-releasing hormone, etc.) and neurotransmitters (e.g., dopamine). Sex steroids potentiate the responsiveness of the somatotrophs to neuroendocrine factors. Somatostatin is the primary inhibitory control of basal and stimulated GH release. Norepinephrine and serotonin also inhibit GH release. Carp GH, a 188Mamino acid peptide with five cysteine residues, controls the rate of-body growth. Treatment with a superactive agonist analog of luteinizing hormone releasing hormone (LHRH) by intraperitoneal injection, esophageal intubation or feeding is effective in stimulating GH release and body growth of grass carp Ctenopharyngodon idella. Injection or feeding with dopamine receptor agonists (e.g., apomorphine) also stimulates GH release and body growth of grass carp. Treatment with recombinant fish GH by injection or feeding significantly increased serum GH levels and growth rate of grass carp. Treatment with LHRHMA, dopamine D-l receptor agonists or exogeneous recombinant GH by feeding constitutes a practical approach to accelerate the growth of cultured carp.