Renal regulation of urea excretion in arousing and homeothermic ground squirrels (Citellus columbianus)

Lesser, R.W; Moy, Richard M.; Passmore, John C.; Pfeiffer, E. W.

doi:10.1016/0010-406x(70)90009-5

Cited by 19 publications

(19 citation statements)

References 8 publications

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“…b) Direct measurements of GFR by inulin clearance and urination in Columbian ground squirrels and jerboa (6,68,76) also support the conclusion that glomerular filtration and urine production is absent or greatly reduced during torpor but increases to near normal during arousal.…”

Section: Measurement Of Renal Function During Hibernationmentioning

confidence: 72%

“…After ϳ12 h, metabolic, heart, and respiratory rates decline, CBT falls again, and the hibernator reenters torpor (53). b) Studies in the Columbian ground squirrel suggest that urine output ceases during torpor (68,75,76) and resumes during arousal and entrance. Since corticomedullary concentration gradients are abolished during torpor, hypertonic urine found in the bladder of a torpid squirrel was presumed to have formed during a prior arousal (76).…”

Section: Measurement Of Renal Function During Hibernationmentioning

confidence: 99%

“…Since corticomedullary concentration gradients are abolished during torpor, hypertonic urine found in the bladder of a torpid squirrel was presumed to have formed during a prior arousal (76). c) In Columbian ground squirrels implanted with a ureteral catheter, urine flow was noted to begin only after rewarming during arousal, and the lowest temperature at which urine flow began was 18°C (68).…”

Section: Measurement Of Renal Function During Hibernationmentioning

confidence: 99%

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Renal adaptation during hibernation

Jani

Martin

Jain

et al. 2013

American Journal of Physiology-Renal Physiology

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Hibernators periodically undergo profound physiological changes including dramatic reductions in metabolic, heart, and respiratory rates and core body temperature. This review discusses the effect of hypoperfusion and hypothermia observed during hibernation on glomerular filtration and renal plasma flow, as well as specific adaptations in renal architecture, vasculature, the renin-angiotensin system, and upregulation of possible protective mechanisms during the extreme conditions endured by hibernating mammals. Understanding the mechanisms of protection against organ injury during hibernation may provide insights into potential therapies for organ injury during cold storage and reimplantation during transplantation.hibernation; kidney; torpor; metabolism; electrolytes MAMMALIAN HIBERNATORS EXHIBIT heterothermy during winter months, cycling through periods of low core body temperature (CBT) for days to weeks (22) during torpor, followed by periodic arousals when CBT is elevated to 37°C for ϳ12 h ( Fig. 1) (63). CBT during torpor can fall to as low as Ϫ3°C in arctic ground squirrels (7) or 2-10°C in temperate-zone hibernators (22). During torpor, hibernators undergo profound physiological changes, reducing their heart rate from a summertime level of 200 -300 to 3-5 beats/min (128), their respiratory rate from 100 -200 to 4 -6 breaths/min (33, 46) and their metabolic rate to as low as 1-5% of basal metabolic rate (47). During arousal, organs undergo rapid metabolic reactivation, reperfusion, and rewarming to near normal levels (22). After maintaining euthermia and high metabolic activity for 12-18 h, the hibernator reenters torpor (Figs. 1 and 2). This review will focus on the renal adaptations employed by hibernators that permit their kidneys to withstand extreme fluctuations in CBT and organ perfusion during winter heterothermy. Studies of hibernation have been conducted for over a century and the nomenclature used to describe the various stages of hibernation, and the criteria used to define stages of hibernation, have evolved. Earlier studies often simply compared "hibernating" with "nonhibernating," and both terms were variably used. Hibernating often meant mid-winter torpor but was also used to refer to animals that were aroused, either naturally or more often, artificially. Nonhibernating was used to denote midsummer euthermic animals or winter aroused animals (94). As a further complication in the nomenclatures used, some investigators examine monthly or seasonal changes whereas others examine changes that occur during one torpor-arousal cycle of a few days duration. More recent studies have employed specific definitions of stages, representing both seasonal and torpor-arousal cycles, based on CBT monitoring using radiotelemetry (62,63,70,83) (Fig. 1). In addition, torpor can occur daily (referred to as "daily torpor" in "daily heterotherms") or over several days to weeks typically during winter in hibernators (46,125). For the purposes of this review we will 1) focus on renal function in hibernators that e...

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Section: Measurement Of Renal Function During Hibernationmentioning

confidence: 72%

Section: Measurement Of Renal Function During Hibernationmentioning

confidence: 99%

Section: Measurement Of Renal Function During Hibernationmentioning

confidence: 99%

See 1 more Smart Citation

Renal adaptation during hibernation

Jani

Martin

Jain

et al. 2013

American Journal of Physiology-Renal Physiology

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“…Bears maintain constant serum calcium levels even though they are anuric and do not eat or drink during hibernation (Nelson, 1987;Floyd et al, 1990), and thus may have evolved the ability to maintain balanced bone remodeling to prevent hypercalcemia during hibernation. In contrast, other hibernators, such as ground squirrels, interrupt torpor bouts with periodic arousals to euthermia, during which they excrete calcium-containing waste (Hock, 1957;Bruce and Wiebers, 1970;Lesser et al, 1970;Pengelley et al, 1971). This provides a potential avenue for calcium and other products of bone catabolism to be excreted from the body, as occurs during other disuse situations such as human bedrest (LeBlanc et al, 1995;Inoue et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…Bears are immobile and do not eat, drink or excrete waste for 5-7 months per year, and therefore are likely to have evolved the ability to maintain balanced bone remodeling (and prevent bone loss) so they can recycle catabolized calcium from the serum back into the skeleton and prevent hypercalcemia. In contrast, small hibernating mammals arouse, raise their body temperature and excrete waste every 3-25days during hibernation (Hock, 1957;Lesser et al, 1970;Carey et al, 2003). Urination, for example, occurs during interbout arousal periods in Columbian ground squirrels (Moy, 1971), and urine produced during hibernation is known to contain calcium (Pengelley et al, 1971;Shackelford and Caire, 1993).…”

Section: Introductionmentioning

confidence: 99%

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) show microstructural bone loss during hibernation but preserve bone macrostructural geometry and strength

McGee‐Lawrence

Stoll

Mantila

et al. 2011

Journal of Experimental Biology

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SUMMARYLack of activity causes bone loss In most animals. Hibernating bears have physiological processes to prevent cortical and trabecular bone loss associated with reduced physical activity, but different mechanisms of torpor among hibernating species may lead to differences in skeletal responses to hibernation. There are conflicting reports regarding whether small mammals experience bone loss during hibernation. To investigate this phenomenon, we measured cortical and trabecular bone properties in physically active and hibernating juvenile and adult 13-lined ground squirrels (Ictidomys tridecemlineatus, previous genus name Spermophilus). Cortical bone geometry, strength and mineral content were similar in hibernating compared with active squirrels, suggesting that hibernation did not cause macrostructural cortical bone loss. Osteocyte lacunar size increased (linear regression, P0.001) over the course of hibernation in juvenile squirrels, which may indicate an osteocytic role in mineral homeostasis during hibernation. Osteocyte lacunar density and porosity were greater (+44 and +59%, respectively; P<0.0001) in hibernating compared with active squirrels, which may reflect a decrease in osteoblastic activity (per cell) during hibernation. Trabecular bone volume fraction in the proximal tibia was decreased (-20%; P0.028) in hibernating compared with physically active adult squirrels, but was not different between hibernating and active juvenile squirrels. Taken together, these data suggest that 13-lined ground squirrels may be unable to prevent microstructural losses of cortical and trabecular bone during hibernation, but importantly may possess a biological mechanism to preserve cortical bone macrostructure and strength during hibernation, thus preventing an increased risk of bone fracture during remobilization in the spring.

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Mitochondrial phenotype of marsupial torpor: Fuel metabolic switch in the Chilean mouse–opossum Thylamys elegans

et al. 2015

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Torpor is a phenotype characterized by a controlled decline of metabolic rate and body temperature. During arousal from torpor, organs undergo rapid metabolic reactivation and rewarming to near normal levels. As torpor progress, animals show a preference for fatty acids over glucose as primary source of energy. Here, we analyzed for first time the changes in the maximal activity of key enzymes related to fatty acid (Carnitine palmitoyltransferase and β-Hydroxyacyl CoA dehydrogenase) and carbohydrate (Pyruvate kinase, Phosphofructokinase and Lactate dehydrogenase) catabolism, as well as mitochondrial oxidative capacity (Citrate synthase), in six organs of torpid, arousing and euthermic Chilean mouse-opossums (Thylamys elegans). Our results showed that activity of enzymes related to fatty acid and carbohydrate catabolism were different among torpor phases and the pattern of variation differs among tissues. In terms of lipid utilization, maximal enzymatic activities differ in tissues with high oxidative capacity such as heart, kidney, and liver. In terms of carbohydrate use, lower enzymatic activities were observed during torpor in brain and liver. Interestingly, citrate synthase activity did not differ thought torpor-arousal cycle in any tissues analyzed, suggesting no modulation of mitochondrial content in T. elegans. Overall results provide an indication that modulation of enzymes associated with carbohydrate and fatty-acid pathways is mainly oriented to limit energy expensive processes and sustain energy metabolism during transition from torpor to euthermy. Future studies are required to elucidate if physiological events observed for T. elegans are unique from other marsupials, or represents a general response in marsupials. J. Exp. Zool. 325A:41-51, 2016. © 2015 Wiley Periodicals, Inc.

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Renal regulation of urea excretion in arousing and homeothermic ground squirrels (Citellus columbianus)

Cited by 19 publications

References 8 publications

Renal adaptation during hibernation

Renal adaptation during hibernation

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) show microstructural bone loss during hibernation but preserve bone macrostructural geometry and strength

Mitochondrial phenotype of marsupial torpor: Fuel metabolic switch in the Chilean mouse–opossum Thylamys elegans

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