SEASONAL-DEPENDENT AND TEMPERATURE-DEPENDENT VARIATION IN CNS ASCORBATE AND GLUTATHIONE LEVELS IN ANOXIA-TOLERANT TURTLES

Citation
Ma. Perezpinzon et Me. Rice, SEASONAL-DEPENDENT AND TEMPERATURE-DEPENDENT VARIATION IN CNS ASCORBATE AND GLUTATHIONE LEVELS IN ANOXIA-TOLERANT TURTLES, Brain research, 705(1-2), 1995, pp. 45-52
Citations number
59
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences
Journal title
ISSN journal
0006-8993
Volume
705
Issue
1-2
Year of publication
1995
Pages
45 - 52
Database
ISI
SICI code
0006-8993(1995)705:1-2<45:SATVIC>2.0.ZU;2-3
Abstract
We determined the ascorbic acid (ascorbate) and glutathione (GSH) cont ents of eight regions of the CNS from anoxia-tolerant turtles collecte d in summer and in winter. Ascorbate was of special interest because i t is found in exceptionally high levels in the turtle CNS. The tempera ture-dependence of CNS ascorbate content was established by comparing levels in animals collected from two geographic zones with different a verage winter temperatures and in animals re-acclimated to different t emperatures in the laboratory. The analytical method was liquid chroma tography with electrochemical detection. Turtle ascorbate levels were 30-40% lower in animals acclimatized to winter (2 degrees C) than to s ummer (23 degrees C) in all regions of the CNS. Similarly, GSH levels were 20-30% lower in winter than in summer. Winter ascorbate levels we re higher in turtles from Louisiana (19 degrees C) than in turtles acc limatized to winter in Wisconsin (2 degrees C). Summer and winter leve ls of ascorbate could be reversed by re-acclimating animals to cold (1 degrees C) or warm (23 degrees C) temperatures for at least one week. CNS water content did not differ between cold- and warm-acclimated tu rtles. Taken together, the data indicated that ascorbate and GSH under go significant seasonal variation and that the catalyst for change is environmental temperature. Steady-state ascorbate content showed a lin ear dependence on temperature, with a slope of 1.5% per degrees C that was independent of CNS region. Lower levels of cerebral antioxidants in turtles exposed to colder temperatures were consistent with the dec reased rate of cerebral metabolism that accompanies winter hibernation . Cerebral ascorbate and GSH levels in the turtle remained similar to or higher than those in mammals, even during winter, however. These fi ndings support the notion that unique mechanisms of antioxidant regula tion in the turtle contribute to their tolerance of the hypoxia-reoxyg enation that characterizes diving behavior.