Urine concentrating ability of arousing and normothermic ground squirrels (Spermophilus columbianus)

Moy, Richard M.; Lesser, R.W; Pfeiffer, E. W.

doi:10.1016/0300-9629(72)90064-3

Cited by 9 publications

(5 citation statements)

References 6 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: 78%

“…In addition, the tubules of small hibernators may be specifically adapted to function at low temperatures early in the arousal process. Tubular reabsorbtion of urea and urinary concentration occurred as efficiently in arousing and active Columbian ground squirrels and more efficiently than in dogs and rats artificially cooled to 25°C (68,76).…”

Section: Electrolytesmentioning

confidence: 94%

“…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%

“…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). 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: 78%

Section: Electrolytesmentioning

confidence: 94%

Section: Measurement Of Renal Function During Hibernationmentioning

confidence: 99%

Section: Measurement Of Renal Function During Hibernationmentioning

confidence: 99%

See 2 more Smart Citations

Renal adaptation during hibernation

Jani

Martin

Jain

et al. 2013

American Journal of Physiology-Renal Physiology

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“…Glomular filtration may either be arrested (Moy 1971;Tempel & Musacchia 1975) or it may continue at a greatly reduced rate (Zatzman & South 1972, 1975Ondrich, Albert & Panuska 1974). During arousal, however, normal renal function resumes and ground squirrels produce a hypertonic urine containing urea (Moy, Lesser & Pfeiffer 1972). Whether urine production and urea excretion occur during torpor or the succeeding arousal, water is required for excretion.…”

Section: Fig 1 the Relation Between The Duration Of Torpor Bouts Anmentioning

confidence: 99%

Periodic arousals in hibernating mammals: is evaporative water loss involved?

1997

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IntroductionWinter presents a severe metabolic challenge to homeotherms. Just as food availability drops to its annual minimum, low ambient temperatures (T a ) increase energy requirements. Many mammals escape this energy bottleneck by hibernating, whereby they reduce body temperature (T b ) usually below 10°C and metabolic rate to a fraction of that of normothermic individuals. The suppression of metabolic rate through torpor has a clear adaptive value when feeding opportunities are sporadic or non-existent and fat reserves are limited. Hibernators, however, do not exploit the energy savings of torpor to the maximum; all hibernators studied to date arouse periodically (Lyman et al. 1982). Although they account for > 75% of the total energy requirement for hibernation (Kayser 1953;Wang 1978;Thomas, Dorais & Bergeron 1990), arousals remain among the least understood of hibernation phenomena.Although numerous factors have been proposed to account for the occurrence and frequency of arousals, these can be broadly grouped under three principal Summary 1. Using existing data on the rate of cutaneous and pulmonary evaporative water loss (EWL) for hibernating Little Brown Bats (Myotis lucifugus) and on the duration of torpor bouts, body temperature (T b ) and oxygen uptake (V O 2 ) of Golden-mantled Ground Squirrels (Spermophilus saturatus), the rate of EWL was modelled for ground squirrels hibernating at ambient temperatures (T a ) of -2, 2, 4 and 8°C. 2. Total EWL showed a curvilinear response to T a , being lowest at 2°C and increasing with both increasing and decreasing T a . EWL at -2°C was about equal to that at 4°C. The duration of torpor bouts showed the same curvilinear response to T a and torpor bout duration at -2°C was similar to that at 4°C (8·5 vs 8·3 days, respectively). 3. At T a ≥ 2°C, where T b of torpid S. saturatus is not metabolically defended, torpor bout duration is significantly related to T b , V O 2 and EWL, with the three variables having similar r 2 values. 4. Using the regression equations generated at T a ≥ 2°C to predict torpor bout durations at -2°C, where T b is metabolically defended, shows that the three variables do not have equivalent predictive abilities. T b and V O 2 predicted torpor bout durations of 15·2 and -40·4 days, respectively, compared with observed durations of 8·5 days at -2°C. EWL predicted torpor bout durations of 8·4 days or only 0·1 days less than that observed at -2°C. 5. The relation between torpor bout duration and total EWL was insensitive to major variations in cutaneous EWL. Over T a ranging from -2°C to 8°C, a stepwise multiple regression including T b , V O 2 and EWL as independent variables identified EWL as the only variable significantly correlated with torpor bout duration. 6. Our analyses suggest that torpor bout duration may be influenced by EWL, indicating that animals may need to obtain free water when they arouse. An analysis of the structural and temperature characteristics of ground squirrel hibernacula suggests that they may function as a biolog...

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Changes in renal morphology and renin secretion in the golden-mantled ground squirrel (Spermophilus lateralis) during activity and hibernation

et al. 1990

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Chronological changes in renal glomerular morphology and plasma renin activity were investigated during active and hibernating periods in the golden-mantled ground squirrel Spermophilus lateralis. The objective of this study was to determine whether the glomerular endothelium, visceral epithelium (podocytes), basement membrane, mesangial cells, proximal convoluted tubule cells and plasma renin activity exhibit measurable sequential differences between as well as within active and hibernating states at various time points. Limitations in the size of the experimental population prevented an evaluation of changes in these parameters during other important periods such as periodic arousal between hibernation bouts. In this study, glomerular endothelial pore number and epithelial filtration slit number significantly decreased by early hibernation when compared to those during summer activity, and then they increased back toward summer levels by late hibernation. In contrast, podocytic pedicel width along the glomerular basement membrane increased from summer activity to early hibernation, before significantly decreasing again by late hibernation. Mesangial cell and proximal convoluted tubule cell activity appeared increased during hibernation as compared to summer activity, whereas the width of the glomerular basement membrane showed no significant alterations throughout. Plasma renin activity significantly increased during early hibernation and mid-hibernation when compared to summer levels but had decreased by late hibernation toward summer values. The glomerular and plasma renin activity changes observed in this study clearly illustrate the drastic structural and functional adjustments which hibernating species make during torpor and also correlate well with the reported decrease in renal perfusion pressure and urine formation during hibernation.(ABSTRACT TRUNCATED AT 250 WORDS)

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Urine concentrating ability of arousing and normothermic ground squirrels (Spermophilus columbianus)

Cited by 9 publications

References 6 publications

Renal adaptation during hibernation

Renal adaptation during hibernation

Periodic arousals in hibernating mammals: is evaporative water loss involved?

Changes in renal morphology and renin secretion in the golden-mantled ground squirrel (Spermophilus lateralis) during activity and hibernation

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