Reduction in amino-acid-induced anti-hypothermic effects during general anesthesia in ovariectomized rats with progesterone replacement

Purpose

The aim of the present study was to determine whether the ovarian hormones, estrogen and progesterone, had different influences on amino-acid-induced anti-hypothermic effects during general anesthesia.

Methods

Ovariectomized Sprague–Dawley female rats were divided into four groups: those administered 17β-estradiol plus saline or an amino acid mixture (E2-Sal and E2-AA, respectively) and progesterone plus saline or an amino acid mixture (P-Sal and P-AA, respectively). Five weeks after ovariectomy, rats were given either E2 or P and then administered either Sal or AA solution for 180 min during anesthesia with sevoflurane. Rectal temperatures were measured.

Results

Rectal temperatures were significantly higher in the E2-AA group than in the E2-Sal group 165 and 180 min after initiating the infusion of the test solutions. However, no significant differences were observed between the P-treated groups. The phosphorylation of 4E-BP1 and S6K1 was significantly greater in the E2-AA group than in the E2-Sal group (P < 0.05, P < 0.001, respectively). In contrast, the phosphorylation of 4E-BP1 was significantly lower in the P-AA group than in the P-Sal group (P < 0.001).

Conclusions

These results suggest that progesterone reduces amino-acid-induced anti-hypothermic effects during general anesthesia.