Effects of Anesthetics and Terminal Procedures on Biochemical and Hormonal Measurements in Polychlorinated Biphenyl Treated Rats

Abstract

This investigation reports the effects of various terminal procedures, and how they modified the responses to a toxicant (polychlorinated biphenyls [A1254], 130 mg/kg/day × 5 days) administered by gavage to Sprague-Dawley male rats. Terminal procedures included exsanguination via the abdominal aorta under anesthesia (isoflurane inhalation or Equithesin injection), decapitation with or without anesthesia, or narcosis induced by carbon dioxide inhalation. Effects of repeated anesthesia were also tested. Terminal procedures induced confounding stress responses, particularly when Equithesin was used. The terminal procedures modified the conclusions about effects of A1254 on the concentrations of corticosterone, insulin, glucagon, glucose, alkaline phosphatase, lactate dehydrogenase, uric acid, and blood urea nitrogen, from nonstatistically significant to significant changes, and in the case of luteinizing hormone from a statistically significant increase to a significant decrease. Investigations of effects of toxicants should be designed and interpreted considering potential changes induced by the selection of a terminal procedure.

Brief anesthesia by isoflurane alters plasma corticosterone levels distinctly in male and female rats: Implications for tissue collection methods

“…The data demonstrate that isoflurane elevated plasma corticosterone levels of female, but not male, rats. Our findings are consistent with those of several other studies using male rats which have reported no changes in corticosterone levels following similar exposures to isoflurane [2, 11, 12]. A substantial body of literature shows that female rats display greater HPA axis activity including higher corticosterone levels compared to males at both baseline and in reaction to an acute stressor [13–15].…”

Differential regulation of pancreatic digestive enzymes during chronic high-fat diet-induced obesity in C57BL/6J mice

“…The levels of glucose at baseline (time 0) were already quite elevated. This was most probably due to the use of an anaesthetic (isoflurane), which induces blood glucose level elevation, as has been reported previously ( 21 , 22 ) . The levels of insulin and glucose following 45 E% diet feeding for 12 weeks indicated that the mice were developing hyperglycaemia or insulin sensitivity reduction, as fasting blood glucose and insulin levels were elevated when compared with those in mice fed the 10 E% diet.…”

Exposure to dexamethasone during late gestation causes female-specific decreases in core body temperature and prepro-thyrotropin-releasing hormone expression in the paraventricular nucleus of the hypothalamus in rats

“…Although these data indicate a potential problem with TH feedback on the PVN, the expression of thyroid receptor-β (THRβ), which is a key receptor involved in TH feedback on the PVN, was not observed to be altered (data not shown). Reports have also indicated that isoflurane anesthesia may decrease peripheral T4 levels in adult male rats [37], but given the short span of time between anesthesia and blood collection in the adult rats in our study, it is unlikely that this explains the inconsistent TH results between juvenile and adult rats. Finally, peripheral TH levels may not reflect the non-neuroendocrine effects mediated by TRH, suggesting that local signaling by this peptide within the brain may be influencing CBT and other metabolic processes.…”