Histone-like protein: a novel method for measuring stress in fish.
We assessed the effect of chronic stress using a group of potent, broad-spectrum antimicrobial polypeptides, called histone-like proteins (HLPs), which appear to be an important component of non-specific immunity in channel catfish Ictalurus punctatus skin. An enzyme-linked immunosorbent assay (ELISA) was developed to measure the predominant HLP (HLP-1) in channel catfish skin. Catfish were then exposed to a chronic stress consisting of overcrowding and elevated ammonia. Healthy unstressed fish had consistently high HLP-1 levels, but fish that had been stressed for 1 wk had significantly depressed HLP-1 levels; HLP-1 levels declined further in fish stressed for 3 or 4 wk. The time-dependent decline in HLP-1 levels was not accompanied by any gross signs of disease. In contrast to HLP-1 levels, antibacterial activity in the skin was significantly greater in fish stressed for 1 wk compared with unstressed fish; in addition, antibacterial activity was the same in fish that were unstressed or stressed for 3 or 4 wk. This suggests that other antibiotics besides HLP-1 may be induced in the skin, especially during early stages of stress, that may compensate for depressed HLP-1 levels. Our results indicate that chronic stress has a significant suppressive effect on HLP-1 levels in channel catfish skin. The reduction of HLP-1 in the absence of clinical signs of disease, combined with evidence that its levels are not affected by the acute stressors of capture or sampling, suggests that HLP levels may be a promising indicator for monitoring fish health.
Robinette
D W
DW
North Carolina State University, College of Veterinary Medicine, Raleigh 27606, USA.
Noga
E J
EJ
D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D004268:DNA-Binding Proteins / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D029968:Escherichia coli Proteins; D005393:Fish Diseases / Q000175:diagnosis*; D007059:Ictaluridae; D012867:Skin / Q000737:chemistry; D013312:Stress, Physiological / Q000175:diagnosis / Q000662:veterinary*; D013997:Time Factors
D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C116822:hns protein, E coli