Is lactate a mediator of hypoxia-induced anapyrexia?

Abstract

Hypoxia causes a regulated decrease in body core temperature ( T(c)), termed anapyrexia, which seems to be a very effective way of preventing hypoxia-associated cell damage. Since during several pathological states the supply of O(2) is a limiting factor, the clinical importance of anapyrexia is evident. However, the mechanisms involved in this response remain unclear. We tested the hypothesis that lactate, a classic companion of hypoxia, is a mediator of hypoxia-induced anapyrexia, using the inhibitor of acid lactic production dichloroacetate (DCA). Each of 28 rats was placed in a chamber ventilated with humidified air at an ambient temperature of 24-26 degrees C. After a control period of 30 min the animals were given saline or 100 mg/kg DCA i.p. Then, 30 min later, the chamber was flushed with a 7% O(2) gas mixture for 2 h. At the end of the experiment, the animals were decapitated and blood samples collected for measurements of plasma lactate. T(c) was measured by biotelemetry. DCA did not affect the T(c) or basal lactate levels of normoxic rats. Hypoxia elicited a significant decrease in T(c) and an increase in plasma lactate levels. Although DCA decreased plasma lactate levels during hypoxia, it caused no change in the course of hypoxia-induced anapyrexia. Correspondingly, no correlation was found between the drop in T(c) and the rise in plasma lactate during hypoxic conditions. These results do not support the hypothesis that lactate is a mediator of hypoxia-induced anapyrexia in rats.

Porcine neonates failing vitality score: physio-metabolic profile and latency to the first teat contact

“…Both traits are related since hypoxia elicits an array of compensatory responses, among them is anapyrexia, the regulated drop of body temperature, which is a very efficient way to prevent cellular damage caused by hypoxia . The general importance of anapyrexia resides in the fact that it reduces the consumption of oxygen and increases the affinity of haemoglobin to oxygen (Bicego et al, 2002;Steiner et al, 2002). Variations in temperature tend to affect the entire organism (Odehnalová et al, 2008); the neonate piglets that obtained a low vitality score showed hypercapnia, results in agreement with previous work by Randall (1971) and Herpin et al (1996); whereas more recently, Groenendaal et al (2009) indicated that hypothermia affects PCO 2 diminishing this gas concentration at low temperatures.…”

Time-dependent effects of exposure to static magnetic field on glucose and lipid metabolism in rat

“…Nonetheless, under SMF, rats exposed during 15 days displayed an increase in lactate concentration. This increase of lactate can be the sign of hypoxia state, as suggested by several authors (Bicego et al 2002;Gargaglioni et al 2003).…”

Thermoregulatory and metabolic responses of Japanese quail to hypoxia

“…Although direct calorimetry is needed to fully address this issue, the observed increase in blood lactate levels during exposure to 9% O 2 supports this hypothesis. Blood lactate levels also increase in rats during acute hypoxia (7% O 2 ) (Bicego et al, 2002); interestingly, there was no correlation between blood lactate levels and T b depression in the rat, suggesting that there is no direct relationship between anaerobic heat production and T b depression in that species. These data suggest that increased thermolysis is principally responsible for the reduced T b during hypoxia in Japanese quail, and perhaps in other birds.…”