Splenic contraction, catecholamine release, and blood volume redistribution during diving in the Weddell seal

Hurford, William E.; Hochachka, P. W.; Schneider, Robert; Guyton, G. P.; Stanek, Krystian; Zapol, D. G.; Liggins, G. C.; Zapol, W. M.

doi:10.1152/jappl.1996.80.1.298

Cited by 107 publications

(99 citation statements)

References 19 publications

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“…Qvist et al (2) recorded a distinct rise in Weddell seal Hct during diving and suggested that the total red cell mass is partitioned between general circulation and the splenic reservoir. The concept of splenic red cell storage is well accepted by many researchers, and a diving-induced sympathetic vasoconstriction is thought to be the stimulus for splenic contraction and subsequent injection of oxygenated RBCs into circulation (2,4,6,7). Strong evidence supports this line of reasoning.…”

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confidence: 96%

“…Dive and postdive catecholamine levels collected from freely diving Weddell and harbor seals show a significant increase over resting levels (6,10,11). In hooded and harp seals, in vitro plethysmographic measurements indicate that ␣-adrenoreceptor activation with epinephrine results in forceful contraction within 1-3 min of administration.…”

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confidence: 99%

“…Strong evidence supports this line of reasoning. Histological and physiological data collected on seal spleens indicate that the organ is capable of considerable RBC storage and that it reacts to catecholamine stimulation (6)(7)(8)(9). The ability of the phocid spleen to concentrate RBCs is supported by high Hct values obtained from splenic venous blood during catecholamine-induced contraction (88-93% in hooded seals; 82-88% in harp seals; ref.…”

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confidence: 99%

“…7). Ultrasound imaging in Weddell seals demonstrates a correlation of the diving-induced rise in Hct with a postdive reduction in spleen size (6).…”

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confidence: 99%

“…The contractile effect of epinephrine and nor-epinephrine was largely abolished when the ␣-adrenergic receptors were first blocked with phentolamine (7). Hurford et al (6) found that, in vivo, Weddell seal spleens contract on stimulation by exogenous epinephrine infusion. The splenic dimensions obtained during the postepinephrine injection period were similar to those obtained from the postdive period.…”

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confidence: 99%

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Effects of forced diving on the spleen and hepatic sinus in northern elephant seal pups

Thornton

Spielman

Pelc

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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In phocid seals, an increase in hematocrit (Hct) accompanies diving and periods of apnea. The variability of phocid Hct suggests that the total red cell mass is not always in circulation, leading researchers to speculate on the means of blood volume partitioning. The histology and disproportionate size of the phocid spleen implicates it as the likely site for RBC storage. We used magnetic resonance imaging on Northern elephant seals to demonstrate a rapid contraction of the spleen and a simultaneous filling of the hepatic sinus during forced dives (P < 0.0001, R 2 ‫؍‬ 0.97). The resulting images are clear evidence demonstrating a functional relationship between the spleen and hepatic sinus. The transfer of blood from the spleen to the sinus provides an explanation for the disparity between the timing of diving-induced splenic contraction (Ϸ1-3 min) and the occurrence of peak Hct (15-25 min). Facial immersion was accompanied by an immediate and profound splenic contraction, with no further significant decrease in splenic volume after min 2 (Tukey-Kramer HSD, P ‫؍‬ 0.05). At the conclusion of the dive, the spleen had contracted to 16% of its predive volume (mean resting splenic volume ‫؍‬ 3,141 ml ؎ 68.01 ml; 3.54% of body mass). In the postdive period, the spleen required 18 -22 min to achieve resting volume, indicating that this species may not have sufficient time to refill the spleen when routinely diving at sea, which is virtually continuous with interdive surface intervals between 1 and 3 min. P hocid seals exhibit a higher hematocrit (Hct) during apnea and diving than during periods of eupneic respiration (1-4). This variation in red cell mass indicates that seals have some method of sequestering red cells during nonapneic events. Bryden and Lim (5) found the Hct values of elephant seal pups to be highly variable and suggested that the spleen acts as a dynamic reservoir for erythrocytes, releasing RBCs into general circulation when required. Qvist et al. (2) recorded a distinct rise in Weddell seal Hct during diving and suggested that the total red cell mass is partitioned between general circulation and the splenic reservoir. The concept of splenic red cell storage is well accepted by many researchers, and a diving-induced sympathetic vasoconstriction is thought to be the stimulus for splenic contraction and subsequent injection of oxygenated RBCs into circulation (2, 4, 6, 7). Strong evidence supports this line of reasoning. Histological and physiological data collected on seal spleens indicate that the organ is capable of considerable RBC storage and that it reacts to catecholamine stimulation (6-9). The ability of the phocid spleen to concentrate RBCs is supported by high Hct values obtained from splenic venous blood during catecholamine-induced contraction (88-93% in hooded seals; 82-88% in harp seals; ref. 7). Ultrasound imaging in Weddell seals demonstrates a correlation of the diving-induced rise in Hct with a postdive reduction in spleen size (6).Dive and postdive catecholamine levels collected fro...

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mentioning

confidence: 96%

mentioning

confidence: 99%

mentioning

confidence: 99%

“…7). Ultrasound imaging in Weddell seals demonstrates a correlation of the diving-induced rise in Hct with a postdive reduction in spleen size (6).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

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Effects of forced diving on the spleen and hepatic sinus in northern elephant seal pups

Thornton

Spielman

Pelc

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

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Vertebrate Respiration and Circulation in Extreme Conditions

Lillywhite¹

2021

Encyclopedia of Life Sciences

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The, acquisition and internal transport of respiratory gases and metabolic fuels depend on linked processes, with design and function related to energetic demands and attributes of the environment. Environmental challenges to these processes reflect variation in the density of gases, temperature and the pressures that prevail in the environmental medium. The limits of vertebrate survival and performance are tested in environments of low oxygen such as soil, mud or water in which animals overwinter sometimes at freezing temperatures; high altitude where the atmospheric density of oxygen is low; and the deeper reaches of ocean where pressure and distance challenge the physiology of air‐breathing vertebrates. Cardiorespiratory functions are also limited by the metabolic demands of animals related to body size, temperature, activity and gravity, which also impacts features of morphology and behaviour. Responses of vertebrates to physical environmental challenges are related to phylogenetic evolutionary changes and include both plasticity of adjustments and genetic/genomic changes influencing form and function, including molecular underpinnings. Key Concepts Aerobic cellular respiration requires internal transport of fuels, oxygen and carbon dioxide, which are exchanged with the external environment and at greater rates during exercise or activity involving muscles. The rate of energy expenditure, or metabolism, per unit of body mass decreases with increasing body size, while increasing with temperature and level of activity. The functional capacities of each step in oxygen transport are matched to each other, and the upper limits to aerobic capacity depend on the integrated function of the linked steps in oxygen transport, rather than any single factor. Saving of energy is related to lowering of body temperature, suppression of metabolism, behavioural reduction of activity and molecular adjustments in fuel usage, among other factors. Countermeasures to gravity's ‘pull’ on blood circulation include tight tissues, relatively nondistending blood vessels, effective neurogenic control of heart and blood vessels and anatomical or behavioural reduction in the vertical length of blood vessels. Increasing altitude reduces the density of oxygen, reduces temperature, increases the diffusion of gases and increases evaporative water loss. The pressure in a fluid column increases with depth as a result of gravity, and increasing pressures in deep water columns compress air spaces, alter the structure of proteins and function of enzymes and decrease the fluidity of membranes. Atmospheric hypoxia limits the distributional range and performance of vertebrates at higher altitudes. Responses to hypoxia may increase the cardiac output and blood flow to tissues, increase the growth of blood vessels, increase blood oxygen capacity and circulating blood volume and adjust metabolic pathways to favour increased efficiency of ATP production. Compared with mammals, birds have superior ability to acquire O 2 and to maintain blood flow to the brain during hypoxia when levels of CO 2 in the blood are reduced. The survival of overwintering ectothermic vertebrates at subzero temperatures is aided by behavioural, physiological and biochemical adaptations that enable animals either to avoid freezing or to tolerate some portion of their body fluids being converted to ice, which is managed by cryoprotectants and antifreeze proteins. Routine dives of diving vertebrates are aerobic, but glycolysis supplements the energy requirements during prolonged submergence or repetitive dives of some species, as well as the low metabolic needs of turtles and frogs hibernating at low temperatures. Vertebrate adaptations for diving deeply include enhanced oxygen reserves primarily in blood, circulation of blood principally to brain and heart, smaller volumes and collapse of the lung to minimize problems associated with buoyancy and the entry into blood of pressurized pulmonary nitrogen, which leads to embolism and the debilitating condition known as the bends. In sea snakes, cardiovascular shunts ‘meter’ the lung oxygen store, lower the partial pressure of oxygen in blood and enable the loss of nitrogen while minimizing the loss of oxygen across the skin.

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Phocid Seals

and¹,

Bodley²

2014

Zoo Animal and Wildlife Immobilization and Anesthesia

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Splenic contraction, catecholamine release, and blood volume redistribution during diving in the Weddell seal

Cited by 107 publications

References 19 publications

Effects of forced diving on the spleen and hepatic sinus in northern elephant seal pups

Effects of forced diving on the spleen and hepatic sinus in northern elephant seal pups

Vertebrate Respiration and Circulation in Extreme Conditions

Phocid Seals

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