Blood gases in hamsters during hypothermia by exposure to He-O2 mixture and cold

Volkert, WA; Musacchia, X. J.

doi:10.1152/ajplegacy.1970.219.4.919

Cited by 23 publications

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“…The high Teff of hamsters possibly indicates the latent power to survive the hypothermia during hibernation. The high Pao2 of hamsters at Tco of 38°C was also shown by LYMAN and HASTINGS (1951) and VOLKERT and MUSACCHIA (1970). VOLKERT and MUSACCHIA (1970) pointed out that the high Pao2, 56.0 Torr was lowered to 50.4 Torr if the blood was sampled without anesthesia of Nembutal.…”

Section: Discussionmentioning

confidence: 66%

“…The above discussion is not decisive because of the uncertainty on the buffer line at 18°C, but presumably the respiratory acidosis is an important factor for the observed decrease in pH p of the hypothermic rats. VOLKERT and MUSACCHIA (1970) reported that the decreases in arterial pH p and Pao2 and the increase in Pao2 were observed in hamsters at Tco of 6°C. Therefore, the failure in respiratory functions observed for rats at 18°C is thought to equally occur in hamsters in deep hypothermia at 6°C.…”

Section: Discussionmentioning

confidence: 95%

“…In particular, alterations in plasma pH are important features of the physiological adjustments accompanying the bodytemperaiure change in animals (RAIN et al, 1975). Plasma pH and blood gases in hypothermia have been extensively studied for hibernators (LYMAN and HASTINGS, 1951;KENT and PEIRCE II, 1967;VOLKERT and MUSACCHIA, 1970). The regulatory mechanisms involved in the acid-base status are not well assessed in hypothermia.…”

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Difference in the mode of acute cold-induced hypothermia between rat and hamster.

1987

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The present work was undertaken to elucidate the underlying causative factors limiting survival in hypothermic rats (non-hibernator) and hamsters (hibernator). A variety of physiological and biochemical parameters were measured for 28 male Wistar rats (205-286 g) and 26 male golden hamsters (85-118 g) before and during induction of hypothermia to colonic temperature (Tco) of 18°C. With progressive decreases in Tco, parallel falls in Vo2, Vco2, and heart rate were observed. In rats, plasma pH (pH) in arterial blood was significantly lowered from 7.453 at Tco of 38°C to 7.327 at Tco of 18°C (p <0.001). From the observations of increased arterial P~o2 and bound CO2 (bicarbonate ion) concentration, together with the unchanged blood lactate, respiratory acidosis caused by hypoventilation was suggested to be responsible for the decrease in pH. In contrast to rats, in hamsters pH , was almost unchanged during the induction of hypothermia, while nearly complete depletion of blood glucose (-84.6%) and liver glycogen (-99.5%) were observed when Tco of 38°C was lowered to 18°C. It is concluded that the decrease in pH p is a limiting factor for rats to survive the deep hypothermia at Tco of 18°C and the exhaustion of carbohydrates as an energy supply for hamsters. Under severe cold, when heat loss surpasses heat production progressive hypothermia will lead to death of homeothermic animals unless properly rectified. Systematic studies of the physiological changes dung hypothermia are necessary to identify the mechanisms for the failure in homeostasis as well as the inability to recover from it. Although many studies have been made on the underlying potential factors limiting survival in the hypothermic state, the cause of death due to acute hypothermia is controversial and still not completely understood (PREWITT et al.,

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Section: Discussionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 95%

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Difference in the mode of acute cold-induced hypothermia between rat and hamster.

1987

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“…This sort of error in the application of the new technique could be the main source of reports on steep longitudinal and transmural PO 2 gradients. Nevertheless, it is necessary to note that, in addition, neglect of thermostabilization of the tissue under study could significantly contribute to the apparent fall of PO 2 in the flowing and stopped blood due to the expected left shift of the oxyhemoglobin dissociation curve caused by a decrease in blood temperature (1,40). Lack of temperature control in the dorsal skinfold chamber caused a decrease in blood temperature from 38°C in the mouse body to 29°C in the tissue observation area (11).…”

Section: Discussionmentioning

confidence: 99%

The rate of O₂loss from mesenteric arterioles is not unusually high

Golub

Song

Pittman

2011

American Journal of Physiology-Heart and Circulatory Physiology

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Golub AS, Song BK, Pittman RN. The rate of O2 loss from mesenteric arterioles is not unusually high. Am J Physiol Heart Circ Physiol 301: H737-H745, 2011. First published June 17, 2011 doi:10.1152/ajpheart.00353.2011The O 2 disappearance curve (ODC) recorded in an arteriole after the rapid arrest of blood flow reflects the complex interaction among the dissociation of O 2 from hemoglobin, O 2 diffusivity, and rate of respiration in the vascular wall and surrounding tissue. In this study, the analysis of experimental ODCs allowed the estimation of parameters of O 2 transport and O2 consumption in the microcirculation of the mesentery. We collected ODCs from rapidly arrested blood inside rat mesenteric arterioles using scanning phosphorescence quenching microscopy (PQM). The technique was used to prevent the artifact of accumulated O 2 photoconsumption in stationary media. The observed ODC signatures were close to linear, in contrast to the reported exponential decline of intra-arteriolar PO 2. The rate of PO2 decrease was 0.43 mmHg/s in 20-m-diameter arterioles. The duration of the ODC was 290 s, much longer than the 12.8 s reported by other investigators. The arterioles associated with lymphatic microvessels had a higher O 2 disappearance rate of 0.73 mmHg/s. The O 2 flux from arterioles, calculated from the average O 2 disappearance rate, was 0.21 nl O2·cmϪ2 ·s Ϫ1 , two orders of magnitude lower than reported in the literature. The physical upper limit of the O 2 consumption rate by the arteriolar wall, calculated from the condition that all O 2 is consumed by the wall, was 452 nl O 2·cm Ϫ3 ·s Ϫ1 . From consideration of the microvascular tissue volume fraction in the rat mesentery of 6%, the estimated respiration rate of the vessel wall was ϳ30 nl O 2·cm Ϫ3 ·s Ϫ1 . This result was three orders of magnitude lower than the respiration rate in rat mesenteric arterioles reported by other investigators. Our results demonstrate that O 2 loss from mesenteric arterioles is small and that the O2 consumption by the arteriolar wall is not unusually large. microcirculation; arterioles; oxygen consumption; phosphorescence quenching microscopy CAPILLARIES PLAY A CENTRAL ROLE in the diffusive O 2 supply to parenchymal cells, as envisioned by Krogh (18,19). For half a century after Krogh's breakthrough, this concept stood as a pillar of experimental research and mathematical modeling of O 2 transport to tissue. Forty years ago, the experimental findings of a longitudinal gradient of PO 2 in arterioles undermined the absolutism of the central role of capillaries and demonstrated the possibility of substantial O 2 loss from blood before it enters the capillaries (5). Longitudinal gradients of O 2 content and partial pressure in arteriolar blood were reported by independent researchers with different measuring techniques (20,21,25,26,37) and were reviewed in Refs. 17 and 38. The contribution of arterioles to the diffusion of O 2 from blood to tissue was established experimentally and received theoretical substantiation (24). Fur...

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“…Some studies show a strategy that approaches ␣-stat (e.g., 66), whereas others suggest pH-stat (e.g., 64). Discrepancies between different studies are likely the result of methodological differences with respect to the induction of hypothermia; some, for example, have used anesthetics (e.g., pentobarbital and halothane) with known effects on V E, thermogenesis, and acid-base status (1,2,40,57).…”

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Acid-base balance in the developing marsupial: from ectotherm to endotherm

Andrewartha

Cummings

Frappell

2014

Journal of Applied Physiology

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Marsupial joeys are born ectothermic and develop endothermy within their mother's thermally stable pouch. We hypothesized that Tammar wallaby joeys would switch from α-stat to pH-stat regulation during the transition from ectothermy to endothermy. To address this, we compared ventilation (Ve), metabolic rate (Vo2), and variables relevant to blood gas and acid-base regulation and oxygen transport including the ventilatory requirements (Ve/Vo2 and Ve/Vco2), partial pressures of oxygen (PaO2), carbon dioxide (PaCO2), pHa, and oxygen content (CaO2) during progressive hypothermia in ecto- and endothermic Tammar wallabies. We also measured the same variables in the well-studied endotherm, the Sprague-Dawley rat. Hypothermia was induced in unrestrained, unanesthetized joeys and rats by progressively dropping the ambient temperature (Ta). Rats were additionally exposed to helox (80% helium, 20% oxygen) to facilitate heat loss. Respiratory, metabolic, and blood-gas variables were measured over a large body temperature (Tb) range (∼15-16°C in both species). Ectothermic joeys displayed limited thermogenic ability during cooling: after an initial plateau, Vo2 decreased with the progressive drop in Tb. The Tb of endothermic joeys and rats fell despite Vo2 nearly doubling with the initiation of cold stress. In all three groups the changes in Vo2 were met by changes in Ve, resulting in constant Ve/Vo2 and Ve/Vco2, blood gases, and pHa. Thus, although thermogenic capability was nearly absent in ectothermic joeys, blood acid-base regulation was similar to endothermic joeys and rats. This suggests that unlike some reptiles, unanesthetized mammals protect arterial blood pH with changing Tb, irrespective of their thermogenic ability and/or stage of development.

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Blood gases in hamsters during hypothermia by exposure to He-O2 mixture and cold

Cited by 23 publications

References 0 publications

Difference in the mode of acute cold-induced hypothermia between rat and hamster.

Difference in the mode of acute cold-induced hypothermia between rat and hamster.

The rate of O₂loss from mesenteric arterioles is not unusually high

Acid-base balance in the developing marsupial: from ectotherm to endotherm

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Blood gases in hamsters during hypothermia by exposure to He-O2 mixture and cold

Cited by 23 publications

References 0 publications

Difference in the mode of acute cold-induced hypothermia between rat and hamster.

Difference in the mode of acute cold-induced hypothermia between rat and hamster.

The rate of O2loss from mesenteric arterioles is not unusually high

Acid-base balance in the developing marsupial: from ectotherm to endotherm

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The rate of O₂loss from mesenteric arterioles is not unusually high