Plasma leucine aminonaphthylamidase as an indicator of acute sublethal toxicant stress in rainbow trout

Abstract

Leucine aminonaphthylamidase (LAN) is a lysosomal enzyme that appears in blood plasma after cell death. Levels of plasma LAN (PLAN) were assayed to quantify toxicant stress in rainbow trout in a series of experiments. Blood samples were taken from groups of fish weighing 80 to 100 g following intraperitoneal (i.p.) and/or waterborne exposure to p‐methylphenol (PMP) or carbon tetrachloride (CCl4). The duration of postinjection holding significantly affected PLAN activity in control and PMP‐dosed rainbow trout; the largest increases occurred after 96 h. There were significant correlations between dose and PLAN activity after both PMP and CCl4 injection. PLAN levels of fish injected with PMP at doses of 0.075 to 0.75 of the 96‐h i.p. LD50 were elevated by 27 to 63% relative to controls 96 h after injection. PLAN levels of fish injected with CCl4 at doses of 0.18 to 0.79 of the i.p. LD50 were elevated by 38 to 135% relative to controls 48 h after injection. Exposure of fish to a waterborne concentration of 0.028 mM PMP (0.41 96‐h LC50) significantly increased PLAN activity after 48, 96 and 192 h; activities increased by 38 to 87% relative to controls. Elevated PLAN activity was strongly correlated with decreased plasma protein levels. The temperature and duration of plasma storage affected the measured PLAN activity of control and PMP‐dosed rainbow trout. While diet modified PLAN activity, the gender of immature fish had no effect. Hepatic lesions visible by light microscope were observed with waterborne PMP exposure; parenchymatous edema was closely associated with increased liver somatic index. There were, however, no visible lesions or changes in the index associated with the pulse i.p. doses of PMP and CCl4. In these cases, biochemical lesions preceded any evidence of histopathology.

Serum sorbitol dehydrogenase activity as an indicator of chemically induced liver damage in rainbow trout

“…Changes in serum protein levels under toxicant stress are poorly understood, but can theoretically result from hemodilution, loss of protein to urine following kidney damage, or increased protein utilization without replenishment. The increased hematocrit shown by fish exposed to CC14 indicates hemodilution, and is consistent with previous work [14]. The absence of altered hematocrit in fish exposed to P and PPP suggests another, as yet unknown, mechanism.…”

Effects of Chemical Contaminants on Blood Chemistry of Teleost Fish: A Bibliography and Synopsis of Selected Effects

“…In another seasonal study with rainbow trout (Kamloops strain), hematocrits decreased from October through March and showed significant sex-related differences between males (46-39%) and females (37-28%) [104]. Other publications (14,20,32,71,79,94,96,98, reported values from 24 to 43%, with one other report as high as 57% [89]. No significant differences in hematocrit were observed in rainbow trout fed a high-or low-carbohydrate diet [96].…”

“…Other publications (14,20,32,71,79,94,96,98, reported values from 24 to 43%, with one other report as high as 57% [89]. No significant differences in hematocrit were observed in rainbow trout fed a high-or low-carbohydrate diet [96]. Hematocrits for coho salmon ranged from 18 to 28% [103,106], brook trout 30 to 48% [74,85], and brown trout 20 to 56% [4, 85,89].…”