The Effect of short-term hyper-ammonia exposure in Indiancatfish, Clarias magur (Hamilton, 1822) on haematological parameters, tissues structure and gene expression profiles

Short term Ammonia exposure effects in catfish

Abstract

 In the present study, pattern of changes in blood physiological parameters, structural
changes in gills, liver and kidnney as well as gene expression patterns for ornithine-urea
cycle (OUC) were studied, under hyper-ammonia stress (25 mM NH4Cl) for 1, 3, 6 and 9 h
and 24 h in normal water condition after 9 h exposure (9h+N), in Clarias magur (Hamilton,
1822). Analysis showed increase in blood ammonia upto 3 h, with decreasing trend (upto
2 folds reduction) subsequently. It was accompanied by simultaneous increase in urea
levels upto 6 folds at 9 h exposure. However, there were no significant changes in blood
parameters, except for serum protein, serum glutamic pyruvic transaminase (SGPT) and
lactate dehydrogenase (LDH) levels after 1 h exposure. Histological analysis of gills revealed
highest (88%) percentage of damaged gills with congested blood capillaries, treated for 9 h,
but declined by 65% at 9h+N. Histological alterations in liver and kidney were prominent
only at 9 h exposure, with nuclear hypertrophy and necrosis of hepatic cells in liver tissues
and distension as well as degeneration of Bowman’s capsule in kidneys. Significant
up-regulation of cpsIII and otc genes at 9 h and 9h+N, points to activation of OUC in liver at
6 h exposure and unique physiological characteristics of turning towards ureotelism from
ammoniotelism, after short term exposure to high ammonia level.

Keywords:
Ammonium chloride; Clarias magur, Congested capillaries, Gills, Hyperplasia, Ornithine urea cycle, Urea