Tissue glycogen levels in the Weddell seal, Leptonychotes weddelli: A possible adaptation to asphyxial hypoxia

Kerem, D; Hammond, D.D; Elsner, Robert

doi:10.1016/0300-9629(73)90076-5

Cited by 58 publications

(18 citation statements)

References 13 publications

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“…In general, skeletal muscle Gly concentrations in diving birds and mammals (31 to 80 mmol kg −1 muscle) are highly varied and similar to concentrations in most terrestrial animals (26 to 71 mmol kg −1 muscle) (Edwards et al 1999; Goforth 1986; Groscolas and Rodriguez 1982; Kerem et al 1973; Saltin and Gollnick 1983). Gly concentrations determined in this study are not notably different from fasting emperor penguins, other birds or mammals (Table 1).…”

Section: Discussionmentioning

confidence: 87%

Muscle Energy Stores and Stroke Rates of Emperor Penguins: Implications for Muscle Metabolism and Dive Performance

Williams¹,

Sato²,

Shiomi³

et al. 2012

Physiological and Biochemical Zoology

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In diving birds and mammals, bradycardia and peripheral vasoconstriction potentially isolate muscle from the circulation. During complete ischemia, ATP production is dependent on the size of the myoglobin oxygen (O2) store and the concentrations of phosphocreatine (PCr) and glycogen (Gly). Therefore, we measured PCr and Gly concentrations in the primary underwater locomotory muscle of emperor penguin and modeled the depletion of muscle O2 and those energy stores under conditions of complete ischemia and a previously determined muscle metabolic rate. We also analyzed stroke rate to assess muscle workload variation during dives and evaluate potential limitations on the model. Measured PCr and Gly concentrations, 20.8 and 54.6 mmol kg−1, respectively, were similar to published values for non-diving animals. The model demonstrated that PCr and Gly provide a large anaerobic energy store, even for dives longer than 20 min. Stroke rate varied throughout the dive profile indicating muscle workload was not constant during dives as was assumed in the model. The stroke rate during the first 30 seconds of dives increased with increased dive depth. In extremely long dives, lower overall stroke rates were observed. Although O2 consumption and energy store depletion may vary during dives, the model demonstrated that PCr and Gly, even at concentrations typical of terrestrial birds and mammals, are a significant anaerobic energy store and can play an important role in the emperor penguin’s ability to perform long dives.

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Section: Discussionmentioning

confidence: 87%

Muscle Energy Stores and Stroke Rates of Emperor Penguins: Implications for Muscle Metabolism and Dive Performance

Williams¹,

Sato²,

Shiomi³

et al. 2012

Physiological and Biochemical Zoology

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“…These findings suggest that in adult seals, as in other mammals, cardiac muscle rarely relies on anaerobic metabolism, instead oxidizing lipids and monocarboxylate fuels, such as lactate, for metabolic heat production (Hochachka, 1981;Murphy et al, 1980). However, seal hearts do differ from those of terrestrial mammals, in that they contain large glycogen stores (Henden et al, 2004;Hochachka, 1981;Kerem et al, 1973), and are able to withstand long periods of anaerobic respiration and reduced coronary blood flow without evidence of ischemic damage (Elsner et al, 1985;Kjekshus et al, 1982), indicating that seal hearts possess additional adaptations to withstand the progressive hypoxemia that accompanies diving that were not measured in this study.…”

Section: Discussionmentioning

confidence: 97%

Development of aerobic and anaerobic metabolism in cardiac and skeletal muscles from harp and hooded seals

Burns

Skomp

Bishop

et al. 2010

Journal of Experimental Biology

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SUMMARYIn diving animals, skeletal muscle adaptations to extend underwater time despite selective vasoconstriction include elevated myoglobin (Mb) concentrations, high acid buffering ability () and high aerobic and anaerobic enzyme activities. However, because cardiac muscle is perfused during dives, it may rely less heavily on Mb,  and anaerobic pathways to support contractile activity. In addition, because cardiac tissue must sustain contractile activity even before birth, it may be more physiologically mature at birth and/or develop faster than skeletal muscles. To test these hypotheses, we measured Mb levels,  and the activities of citrate synthase (CS), -hydroxyacyl-CoA dehydrogenase (HOAD) and lactate dehydrogenase (LDH) in cardiac and skeletal muscle samples from 72 harp and hooded seals, ranging in age from fetuses to adults. Results indicate that in adults cardiac muscle had lower Mb levels (14.7%),  (55.5%) and LDH activity (36.2%) but higher CS (459.6%) and HOAD (371.3%) activities (all P<0.05) than skeletal muscle. In addition, while the cardiac muscle of young seals had significantly lower [Mb] (44.7%)  (80.7%) and LDH activity (89.5%) than adults (all P<0.05), it was relatively more mature at birth and weaning than skeletal muscle. These patterns are similar to those in terrestrial species, suggesting that seal hearts do not exhibit unique adaptations to the challenges of an aquatic existence.

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“…Yet the body contains only minuscule amounts of carbohydrate in the form of blood sugar and tissue glycogen, typically less than 0.5% of body mass (Kemp and Van Heijningen 1954;Kerem et al 1973;Flatt 1995). Weddell seals consume a diet of marine fish and invertebrates (Dearborn 1965;Casaux et al 1997Casaux et al , 2006Casaux et al , 2009Lake et al 2003) that is expected to contain very low levels of available carbohydrate (≤0.5% by mass) in the form of glycogen (MacPherson 1932;Oehlenschläger 1991;Rosa et al 2005).…”

Section: Milk Carbohydrate and Its Functional Significancementioning

confidence: 99%

Milk Composition in the Weddell SealLeptonychotes weddellii: Evidence for a Functional Role of Milk Carbohydrates in Pinnipeds

Eisert¹,

Oftedal²,

Barrell³

2013

Physiological and Biochemical Zoology

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We propose that secretion of milk sugar has important consequences for the metabolic economies of lactating phocid seals and their pups. Milk was collected from 21 Weddell seals Leptonychotes weddellii in McMurdo Sound, Antarctica, and assayed by standard methods. Milk composition changed over the course of lactation, but at mid- to late lactation (16-40 d postpartum), Weddell seal milk composition was relatively constant at 33.8% +/- 0.82% water, 54.0% +/- 0.80% fat, 10.1% +/- 0.16% crude protein, 0.84% +/- 0.03% sugar, 0.75% +/- 0.02% ash, and 23.3 +/- 0.3 kJ g−1 whole milk (WM). At this stage, milk composition varied among individual seals in all assayed constituents except ash. The concentration of sugar in the aqueous phase of Weddell seal milk ( 24.9 +/- 0.6g sugar L−1 water) was ca. 44%-77% of levels found in terrestrial carnivores, indicating that the low sugar concentration of WM is primarily due to its high fat content, not alteration of the aqueous phase. In early lactation, fasting Weddell seals were estimated to devote 39 g d(-1) glucose to milk sugar synthesis, an amount similar to the estimated demand of the maternal brain. This additional glucose demand must be covered by gluconeogenesis in fasting animals and represents a considerable additional drain on maternal resources. However, provision of sugar to offspring at rates sufficient to meet neonatal substrate requirements appears to be essential for efficient fat and protein deposition and thus may be an important component of the phocid reproductive strategy of rapid growth and early weaning.

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Tissue glycogen levels in the Weddell seal, Leptonychotes weddelli: A possible adaptation to asphyxial hypoxia

Cited by 58 publications

References 13 publications

Muscle Energy Stores and Stroke Rates of Emperor Penguins: Implications for Muscle Metabolism and Dive Performance

Muscle Energy Stores and Stroke Rates of Emperor Penguins: Implications for Muscle Metabolism and Dive Performance

Development of aerobic and anaerobic metabolism in cardiac and skeletal muscles from harp and hooded seals

Milk Composition in the Weddell SealLeptonychotes weddellii: Evidence for a Functional Role of Milk Carbohydrates in Pinnipeds

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