Chronobiological study of sex differences in the internal environment in zoletil-anaesthetized rats

ABSTRACT

Although it is generally assumed that females are not significantly more variable than males, there are studies that have demonstrated that differences may be quite large. The aim of the present in vivo study was to determine the effect of general anaesthesia on the status of acid–base balance in spontaneously breathing rats of both sexes in dependence on the light–dark cycle. The experiments were performed using zoletil-anaesthetized (30mg/kg [intraperitoneal], Virbac, France) female and male Wistar rats, after a four-week adaptation to a light–dark cycle (12 h:12 h). The animals were divided into four experimental groups according to sex and light period (n = 20). The results demonstrated sex differences in acid–base balance, as well as sex-related differences between the light and dark period in zoletil-anaesthetized rats. Both females and males exhibited the same tendency toward changes in the status of acid–base balance in both light periods. The most unfavourable status in the internal environment was exhibited in males during the light period (the lowest pH, the most pronounced hypoxia and hypercapnia), but with the maintenance of light–dark differences. The light–dark differences in paO₂ and paCO₂ were eliminated in females, not in males. The optimal status of acid–base balance occurred during the dark period in males.

KEYWORDS:

• Chronobiology
• anaesthesia
• acid-base balance
• sex
• rats

Disclosure statement

No potential conflict of interest was reported by the authors.