Growth Inhibition, Gluconeogenesis, and Morphometric Studies of the Pituitary and Interrenal Cells of Acid-Stressed Brook Trout (Salvelinus fontinalis)

Abstract

Somatic growth was stunted in yearling brook trout (Salvelinus fontinalis) maintained for up to 73 d in pH 4.5. Plasma cortisol level increased in pulses after 1.5 h (from 10 to 82.3 ng∙mL−1) on days 4 (46 ng∙mL−1) and 15–30 (20–25 ng∙mL−1) of acid treatment. Interrenal nuclear hypertrophy and cell hyperplasia occurred respectively on days 4 and 15. Electron microscopic observations revealed that the somatotropes and thyrotropes were atrophic for about half of the experimental period whereas the corticotropes displayed sustained hypertrophy. Plasma glucose and amino acid levels rose simultaneously by 300–600 and 130%, respectively, from day 4 of acid exposure. Hepatic L-alanine aminotransferase activity increased on day 30 just as plasma protein concentration began to decline. When adrenalin and cortisol acetate were administered to trout maintained in neutral pH to raise circulating cortisol levels from 10–20 to 1876 ng∙mL−1, blood glucose remained normal up to 6 d after treatment. These results suggested that acid stress suppressed somatotropin, thyrotropin, and indirectly thyroid hormone secretion but stimulated the pituitary–interrenal axis, leading to inhibition of protein synthesis and accumulation of amino acids in the circulation. The elevation of blood sugar level was caused by some as yet unidentified factors.

Lead-induced metabolic imbalances and feeding alterations in juvenile fathead minnows (Pimephales promelas)

“…When taken as a whole, animals who eat less, require greater effort to obtain food (implying a potential energy imbalance), and defecate more (implying that less of the food is used to build muscle and bone mass) should be expected to grow less. These observations concur with data from other workers indicating that exposure to environmental contaminants results in decreased growth rates (Tam et al, 1988;Seim et al, 1983). Pb-induced changes in growth rates may also be affected by indirect mechanisms, e.g., increased oxygen demands, greater apparent SDA (Weber and Spieler, 1994), and lowered serum thyroxine levels .…”

“…Environmental contaminants, such as Pb, have been shown to affect both growth rates and metabolic activity (Tam et al, 1988;Sawicka-Kapusta et al, 1987;Kumaraguru and Beamish, 1986;Kearns and Atchison, 1979). Because Pb-altered behaviors may be potentially affected by changes in energy allocation and utilization (Weber, 1991), this study was designed to evaluate selected aspects of both behavioral and bioenergetic toxicity as a first step toward integrating these two fields.…”

Glycolysis and gluconeogenesis in the liver of catfish fed with different concentrations of proteins, lipids and carbohydrates

“…Similar results are observed in S. aurata and O. mykiss fed with high levels of protein (Caseras et al 2002;Metón et al 2003). The gluconeogenic pathway is widely reported in liver and also in other tissues (Tam et al, 1998). Gluconeogenesis is an important strategy to regulate the blood glucose concentration, even in fish.…”

Histological changes in insulin-immunoreactive pancreatic ?-cells, and suppression of insulin secretion and somatotrope activity in brook trout (Salvelinus fontinalis) maintained on reduced food intake or exposed to acidic environment

“…For ultrastructural examination of the somatotropes in experiment 2, the pituitaries were dissected and prepared for electron microscopy as described previously Tam et al 1988). For morphometric analyses, electron micrographs of the somatotropes were printed at a magnification of 3240.…”

“…Suppression of somatic growth, reduced food intake and persistently high circulating levels of glucose are some of the most frequently observed effects of exposure to low environmental pH in teleost fishes (Menendez 1976;Brown et al 1984;Lacroix 1985;Tam et al 1988). Experimental evidence has suggested that the very high concentrations of glucose maintained in the plasma of chronically acidstressed fish could not be completely attributed to the increased secretion of corticosteroids and catecholamines that arise upon exposure to acid ) and other forms of stress (Leach and Taylor 1980).…”