Differential vascular adaptive response to stress exposure in male and female rats: Role of gonadal hormones and endothelial cells

Figures & data

Table I.  Effects of gonadectomy and gonadal hormonal replacement on rat body, uterus, vas deferens, seminal vesicle and aorta weights.

		Weight (g)^*
Experimental group		Body	Uterus	Vas deferens	Seminal vesicles	Thoracic aorta
Male	Intact	346.2 ± 10.4	–	0.49 ± 0.01	1.09 ± 0.04	0.032 ± 0.001
	Orchiectomized	446.1 ± 7.0^†	–	0.25 ± 0.01^†	0.14 ± 0.01^†	0.031 ± 0.001
	Orchiectomized plus	364.5 ± 12.2	–	0.44 ± 0.02	1.01 ± 0.06	0.033 ± 0.001
	Testosterone
Female	Intact	271.9 ± 5.4	0.69 ± 0.02	–	–	0.027 ± 0.001
	Ovariectomized	283.8 ± 4.2	0.29 ± 0.01^†	–	–	0.028 ± 0.001
	Ovariectomized plus	287.6 ± 4.4	0.68 ± 0.02	–	–	0.027 ± 0.001
	17β-estradiol

* Values are means ± SEM

^† P < 0.05 vs. the respective intact group. Gonadal hormonal replacement: testosterone, 0.1 mg/rat, once a day for 14 days; 17β-estradiol, 100 μg/kg, once a day for 14 days. All studies were performed at the age of 18 weeks. Animal number range = 6–7 per group.

Figure 1 Effects of noradrenaline on two rings, one with and the other without endothelium, of the same thoracic aorta isolated from control and experimental male rats. The experimental protocols were: (a) stress (2 h-immobilization), (b) orchiectomy ORX, (c) (ORX) plus stress, (d) ORX plus testosterone (test), and (e) ORX plus test plus stress. The removal of endothelium increased maximum response to noradrenaline (P < 0.05), except in orchiectomized non-stressed males (panel b). None of the experimental protocols altered the vascular smooth muscle reactivity to noradrenaline vs. respective controls (see denuded aorta responses, P>0.05). Stress decreased and ORX increased the intact aorta maximum response to noradrenaline (panels a and b, respectively). ORX did not prevent the decrease in the intact aorta reactivity to noradrenaline induced by stress (panels c × b). The maximum response to noradrenaline in intact aorta from stress-exposed orchiectomized rats (panel c, filled triangle) was significantly different from non-stressed intact males (panel c, filled circle). Testosterone treatment restored the intact aorta reactivity to noradrenaline in orchiectomized non-stressed males (panels d × b) and also recovered the stress response in aorta from orchiectomized rats (see panels e, c and a). Values are means ± SEM. *P < 0.05 vs. respective controls. Animal number range = 6–12 per group.

Figure 2 Effects of noradrenaline on two rings, one with and the other without endothelium, of the same thoracic aorta isolated from control and experimental female rats. The experimental protocols were: (a) stress (2 h-immobilization), (b) ovariectomy (OVX), (c) OVX plus stress, (d) OVX plus 17β-estradiol (E₂), and (e) OVX plus E₂ plus stress. The removal of endothelium increased maximum response to noradrenaline (P < 0.05), except in ovariectomized non-stressed females (panel b). None of the experimental protocols altered the vascular smooth muscle reactivity to noradrenaline vs. respective controls (see denuded aorta responses, P>0.05). Stress decreased and OVX increased maximum response to noradrenaline in the intact aorta (panels a and b, respectively). OVX did not prevent the decrease in the intact aorta reactivity to noradrenaline induced by stress (panels c × b). The maximum response to noradrenaline in the intact aorta from stress-exposed ovariectomized rats (panel c, filled triangle) was not significantly different from non-stressed intact females (panel c, filled circle). 17β-estradiol treatment restored the intact aorta reactivity to noradrenaline in ovariectomized non-stressed females (panels d × b) and recovered the stress response in aorta from ovariectomized rats (see panels e, c and a). Values are means ± SEM. *P < 0.05 vs. respective controls. Animal number range = 6–14 per group.

Table II.  Effects of gonadectomy and gonadal hormonal replacement on the EC50 values for noradrenaline obtained for two rings, one with and the other without endothelium, of the same thoracic aorta from male and female rats, submitted or not to stress.

		EC50 ( × 10^− 8 M)^*
		Male		Female
Experimental group		With endothelium	Without endothelium	With endothelium	Without endothelium
Intact (14 weeks)	Non-stressed	2.41 (0.66–8.74)	0.63 (0.33–2.47)^†	7.93 (4.66–13.52)	0.68 (0.42–1.11)^†
	Stressed	23.12 (14.35–32.24)^‡¶	0.71 (0.31–1.67)^†	5.96 (3.53–10.07)	1.05 (0.76–2.40)^†
Intact (16 weeks)	Non-stressed	3.80 (0.80–17.98)	0.77 (0.33–1.77)^†	7.36 (3.72–14.59)	0.62 (0.31–1.22)^†
Gonadectomized	Non-stressed	4.54 (1.30–15.84)	0.52 (0.25–1.06)^†	9.63 (4.06–19.13)	1.15 (0.43–3.07)^†
	Stressed	4.82 (0.85–14.47)	0.34 (0.15–2.07)^†	9.45 (5.35–16.71)	1.01 (0.65–4.22)^†
Intact (18 weeks)	Non-stressed	1.88 (0.57–6.27)	0.18 (0.13–1.77)^†	6.06 (3.36–15.23)	0.66 (0.35–1.04)^†
Gonadectomized plus	Non-stressed	4.52 (2.31–11.48)	1.38 (0.62–3.08)^†	10.86 (3.63–28.64)	1.68 (0.74–3.82)^†
Hormone replacement	Stressed	12.86 (6.41–28.79)^‡¶	1.03 (0.48–2.19)^†	7.17 (4.43–11.64)	1.27 (0.61–2.67)^†

* Values represent geometric means with 95% confidence intervals

^† P < 0.05 vs. the respective group with endothelium

^‡ P < 0.05 vs. the respective non-stressed intact group

^¶ P < 0.05 vs. respective female group. Stress: 2h-immobilization. Gonadal hormonal replacement: testosterone, 0.1 mg/rat, once a day for 14 days; 17β-estradiol, 100 μg/kg, once a day for 14 days. Animal number range = 6–14 per group.

Table III.  Maximal responses and EC50 values to noradrenaline obtained in two rings, one with and the other without endothelium, of the same thoracic aorta from intact male and female rats, submitted or not to stress, in the presence of l-NAME or indomethacin.

		Maximum response (g of tension)^*		EC50 ( × 10^− 8 M)^†
Experimental group		With endothelium	Without endothelium	With endothelium	Without endothelium
Female
Intact	Non-stressed	4.63 ± 0.12	5.92 ± 0.33^‡	5.10 (1.62–13.52)	0.50 (0.14–1.76)^‡
	Stressed	3.42 ± 0.12^¶	5.60 ± 0.49^‡	4.87 (2.55–9.26)	0.52 (0.08–3.12)^‡
Intact +l-NAME	Non-stressed	6.08 ± 0.45	5.97 ± 0.30	0.52 (0.07–3.93)^§	0.55 (0.10–3.14)
(3 × 10^− 4 M)	Stressed	5.78 ± 0.65	5.77 ± 0.37	0.19 (0.03–1.14)^§	0.64 (0.09–4.37)
Intact+indomethacin	Non-stressed	4.17 ± 0.18	5.93 ± 0.11^‡	4.02 (1.57–7.99)	0.83 (0.09–7.29)^‡
(10^− 5 M)	Stressed	3.08 ± 0.19^¶	5.65 ± 0.52^‡	6.45 (2.92–10.57)	0.92 (0.12–6.96)^‡
Male
Intact	Non-stressed	3.64 ± 0.08	4.77 ± 0.21^‡	5.21 (2.03–14.12)	1.35 (0.35–5.24)^‡
	Stressed	2.50 ± 0.10^¶	5.20 ± 0.42^‡	18.38 (12.62–26.79)^¶	0.54 (0.17–1.67)^‡
Intact+l-NAME	Non-stressed	4.93 ± 0.33	5.10 ± 0.34	0.60 (0.16–2.26)^§	0.30 (0.05–1.58)
(3 × 10^− 4 M)	Stressed	4.82 ± 0.34	4.98 ± 0.47	0.56 (0.12–2.55)^§	0.81 (0.10–6.44)
Intact+indomethacin	Non-stressed	3.14 ± 0.15	4.06 ± 0.09^‡	4.25 (1.01–16.77)^¶	0.18 (0.05–1.74)^‡
(10^− 5 M)	Stressed	1.69 ± 0.23^¶	3.66 ± 0.39^‡	19.82 (13.99–28.05)^¶	0.11 (0.02–1.66)^‡

* Values are means ± SEM

^† Values represent geometric means with 95% confidence intervals. l-NAME = N^ω-nitro-l-arginine methyl ester. Stress: 2h-immobilization

^‡ P < 0.05 vs. the respective group with endothelium

^¶ P < 0.05 vs. the respective non-stressed group

^§ P < 0.05 vs. the respective group in the absence of l-NAME. Animal number range = 6–9 per group.