Influence of exogenous and endogenous estrogen on thermoregulatory responses to mild heat and the interaction with light and dark phases

Table 2 Average measurements of the whole day and the light and dark phases and the circadian amplitude on the control day

Group	Average of the whole day	Average of the light phase	Average of the dark phase	Amplitude
T_abd, °C
OVX	37.5 ± 0.1	37.3 ± 0.1	37.8 ± 0.1^§	0.6 ± 0.1
OVX + E₂	37.6 ± 0.1	37.3 ± 0.1	37.9 ± 0.1^§	0.6 ± 0.1
D	37.8 ± 0.1	37.4 ± 0.1	37.9 ± 0.1^§	0.5 ± 0.1
P	37.6 ± 0.1	37.3 ± 0.1	37.9 ± 0.1^§	0.6 ± 0.1
T_tail, °C
OVX	34.0 ± 0.6	34.4 ± 0.4	33.5 ± 0.7	0.9 ± 0.3
OVX + E₂	32.3 ± 0.7	33.8 ± 0.5	29.7 ± 0.8*^§	3.4 ± 0.7*
D	34.6 ± 0.3	35.3 ± 0.2	34.0 ± 0.4	1.3 ± 0.2
P	33.7 ± 0.3	34.8 ± 0.3	32.7 ± 0.3^†§	2.1 ± 0.1^†
Spontaneous activity, au
OVX	2.0 ± 0.2	1.1 ± 0.2	2.9 ± 0.4^§	1.8 ± 0.4
OVX + E₂	2.4 ± 0.4	1.4 ± 0.3	3.3 ± 0.5^§	1.8 ± 0.3
D	1.5 ± 0.4	1.0 ± 0.4	2.7 ± 0.3^§	1.8 ± 0.2
P	2.2 ± 0.2	1.2 ± 0.2	2.9 ± 0.4^§	1.8 ± 0.3
\(\dot{\text {V}}\)O₂, ml min⁻¹ kg bw^−0.75
OVX	15.1 ± 0.3	13.6 ± 0.6	16.5 ± 0.9^§	3.3 ± 1.3
OVX + E₂	14.5 ± 0.6	12.1 ± 0.9	16.8 ± 0.4^§	4.7 ± 0.7
D	13.3 ± 0.4	12.4 ± 0.7	14.1 ± 0.7^§	1.9 ± 0.9
P	14.7 ± 0.3	14.0 ± 0.4	15.4 ± 0.7^§	1.6 ± 0.9

Data are presented as means ± standard error
OVX, ovariectomized; E₂, estradiol; D, control rats in the diestrus phase; P, control rats in the proestrus phase; T_a, ambient temperature; T_abd, abdominal temperature; T_tail, tail skin temperature; bw, body weight; au, arbitrary unit
* Significant difference from the value in the OVX group, P < 0.05
^†Significant difference from the value in the D group, P < 0.05
^§ Significant difference between the light and dark phases, P < 0.05

ISSN: 1880-6562