title: Acute handling disturbance modulates plasma insulin-like growth factor binding proteins in rainbow trout (Oncorhynchus mykiss).
abstract: The effects of acute stressor exposure on proximal (growth hormone [GH]) and distal (insulin-like growth factor-I [IFG-I] and insulin-like growth factor-binding proteins [IFGBPs]) components of the somatotropic axis are poorly understood in finfish. Rainbow trout (Oncorhynchus mykiss) were exposed to a 5-min handling disturbance to mimic an acute stressor episode, and levels of plasma GH, IGF-I, and IGFBPs at 0, 1, 4, and 24 h post-stressor exposure were measured. An unstressed group was also sampled at the same clock times (09:00, 10:00, 13:00, and 08:00 [the following day]) as acute stress sampling to determine temporal changes in the above somatotropic axis components. The acute stressor transiently elevated plasma cortisol and glucose levels at 1 and 4 h post-stressor exposure, whereas no changes were seen in the unstressed group. Plasma GH levels were not affected by handling stress or sampling time in the unstressed animals. Plasma IGF-I levels were significantly depressed at 1 and 4 h post-stressor exposure, but no discernible temporal pattern was seen in the unstressed animals. Using a western ligand blotting technique, we detected plasma IGFBPs of 21, 32, 42, and 50 kDa in size. The plasma levels of the lower-molecular-weight IGFBPs (21 and 32 kDa) were unaffected by handling stressor, nor were there any discernible temporal patterns in the unstressed animals. By contrast, the higher-molecular-weight IGFBPs (42 and 50 kDa) were affected by stress or time of sampling. Levels of the 42-kDa IGFBP levels significantly decreased over the sampling period in unstressed control animals, but this temporal drop was eliminated in stressed animals. Levels of the 50-kDa IGFBPs also decreased significantly over the sampling time in unstressed trout, whereas handling disturbance transiently increased levels of this IGFBP at 1 h but not at 4 and 24 h post-stressor exposure compared with the control group. Overall, our results suggest that acute stress adaptation involves modulation of plasma IGF-1 and high-molecular-mass IGFBP levels (42 and 50 kDa) in rainbow trout.
authors.affiliation: USDA/ARS/Great Lakes WATER Institute, Milwaukee, WI 53204, USA. brian.shepherd@ars.usda.gov
authors.forename: B S
authors.initials: BS
authors.lastname: Shepherd
authors.forename: N
authors.initials: N
authors.lastname: Aluru
authors.forename: M M
authors.initials: MM
authors.lastname: Vijayan
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D013006:Growth Hormone / Q000097:blood; D006854:Hydrocortisone / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000097:blood* / Q000502:physiology; D011897:Random Allocation; D013312:Stress, Physiological / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D006854:Hydrocortisone