Relationship between food availability, glycerol and glycogen levels in low-temperature challenged rainbow smelt Osmerus mordax

Abstract

SUMMARY Rainbow smelt Osmerus modax accumulate glycerol in winter that serves as an antifreeze. Fish were held at 8°C, or subjected to a decrease in water temperature to –1°C over a 19 day period, and subsequently maintained at –1°C from 15 January to 11 May 2004. Starved fish did not survive the challenge of temperature decrease, with death ensuing above the typical freeze point for marine teleosts (–0.8°C). A decrease in temperature activates the glycerol accumulation mechanism at about 5°C with peak plasma levels exceeding 300 μmol ml–1. Glycerol levels begin to decrease in late February even at water temperatures below–1°C, suggesting either an inherent circannual or photoperiod trigger, possibly in association with sufficiently high levels of antifreeze protein. Glycogen levels in liver did not change significantly in starved fish maintained at 8°C. However, liver glycogen was depleted in fish subjected to the low-temperature challenge and at a faster rate in starved than in fed fish. Stored glycogen in liver and other tissues can account for only a small amount of the total glycerol production, suggesting a strong requirement for food during accelerated glycerol production. Liver glycogen levels increased in April and May in association with the decrease in glycerol. Levels of glycerol in liver, kidney, spleen, gill, intestine, heart, muscle and brain follow the same pattern as that in plasma. During the early part of the glycerol accumulation phase, all tissues except for liver have lower levels of glycerol in the intracellular space than the levels in plasma. In liver,glycerol is in equilibrium between the two compartments.

Glycerol loss to water exceeds glycerol catabolism via glycerol kinase in freeze-resistant rainbow smelt (Osmerus mordax)

“…These patterns are also very similar to the one reported by Lewis et al (17), all of them closely fitting one on each other. The predictable decrease in glycerol levels observed in February supports the hypothesis that the decrease of glycerol levels from midFebruary is not triggered by temperature but by some other factor, such as photoperiod (7).…”

“…An elevated GK activity at the end of the cycle might be related to the restoration of glycogen stores in liver suggested previously (7). Regulation of GK activity may be controlled by small increases in water temperature above the winter minima.…”

“…A drop of temperature was determined as the trigger of glycerol accumulation, while a change in the photoperiod is more likely the trigger for the decrease in plasma glycerol reported from late January/late February (3,7). Liver is the major site of production for the entire animal (reviewed in Ref.…”

Effect of various dietary fats supplementation on the liver glycogen, protein and digestive enzymes activities in striped murrel, Channa striatus

“…It is found that the variation in liver glycogen content was changing not in a fashion on addition of various fat content in the diet. Similar studies on the glycogen content estimated by many authors [11][12][13][14][15]. Digestive enzyme pattern of two stomachless filter feeders, silver carp, Hypophthalmichthys molitrix Val., and bighead carp, Aristichthys nobilis has been reported [41].…”

“…Email:ppsicar @ gmail.com, Fax : 91-22 26361573; ph: 91-22-26361446 like Johnston and Goldspink [11] in crucian carp; Driedzic and Short [12] in rainbow smelt; Diwan et al [13]; Peres and OlivaTeles [14] in European seabass and Bakthavatsalam and Reddy [15] in climbing perch. Similarly studies dealing with effect of feeding various lipids through diets on the muscle protein and intestinal protease in fish tissues have been reported by many authors [16][17][18][19].…”