Congenital absence of vasopressin and age-dependent changes in ACTH and corticosterone stress responses in rats

Figures & data

Figure 1.  Serum hormone concentrations in 10-day-old and adult Brattleboro (di/di) rats after single (E; 3 min ether+7 min rest) or repeated (EE; 3 min ether+57 min rest+3 min ether+7 min rest) ether inhalation. In heterozygous controls, both single and repeated ether exposure induced a significant elevation of the ACTH concentrations both in pups (A) and adults (C). The increase after ether exposure was similar in di/di and di/+ adults; however, in di/di pups this elevation was much less than in di/+ pups (A). In pups, only the repeated ether inhalation increased the serum corticosterone concentrations (B), while in adults the single stimulus was also sufficient (D). There was no difference in corticosterone concentrations between the genotypes except for overall greater concentrations in di/di than in di/+ pups. Data are expressed as mean ± SEM. Statistical analysis was done by three-way ANOVA (age, genotype, stress). n = 12–21 per group. **p < 0.01 vs. control; ^##p < 0.01 vs. di/+.

Figure 2.  Serum hormone concentrations in 10-day-old and adult Brattleboro rats 2 h after ip LPS (100 μg/ml/kg) or vehicle (control) injection. In di/+ rats, the LPS injection significantly increased ACTH (A,C) and corticosterone (B, D) concentrations at both ages. The vasopressin deficiency prevented the ACTH increase (A) and induced greater overall corticosterone concentrations (B) in pups, but had no effect on the responses to LPS in adults. Data are expressed as mean ± SEM. Statistical analysis was done by three-way ANOVA (age, genotype, stress). n = 6–15 rats per group. **p < 0.01 vs. control; ^##p < 0.01 vs. di/+.

Figure 3.  Serum hormone concentrations in 10-day-old and adult homozygous vasopressin producing (+/+) Brattleboro rats 15 min after pretreatment with a V_1b antagonist (SSR149415; 10 mg/1 ml/kg or saline with few drops of Tween 80) and 2 h after LPS (100 μg/ml/kg) injection. LPS induced significant increases in serum ACTH (A, B) and corticosterone (C, D) concentrations. The V_1b antagonist pretreatment diminished the ACTH increase in pups (A) but not in adults (B). Data are expressed as mean ± SEM. Statistical analysis was done by three-way ANOVA (age, V_1b treatment, stress). n = 8–16 rats per group. **p < 0.01 vs. control for LPS injection; ^##p < 0.01 vs. control for V_1b injection.

Figure 4.  In vitro CRH sensitivity of anterior pituitary glands of 10-day-old (A) and adult (B) di/+ and di/di Brattleboro rats. In all rats, the 10^{− 10} M CRH significantly increased ACTH secretion, however this increase was much smaller for anterior pituitaries from pups (A). In pups, there was no difference between the genotypes, while in adults the di/di rats had reduced reactivity. The overall amount secreted is represented by the AUC parameter in the inserts. Data are expressed as mean ± SEM. Statistical analysis was done by repeated measure ANOVA (age, genotype, time) or two-way ANOVA (age, genotype). n = 7–13 ^##p < 0.01 vs. di/+.

Figure 5.  In vitro ACTH sensitivity of the adrenal cortex of 10-day-old (A) and adult (B) di/di and di/+ Brattleboro rats. The 10^{− 12} M ACTH significantly increased corticosterone secretion in all groups. The lesser secretion in A compared with B is accounted for by the smaller pup adrenals. In pups, the di/di rats were more reactive to the stimulus (A) in the two post-stimulation fractions but not in the case of the whole secreted amount represented by AUC in the insert. Data are expressed as mean ± SEM. Statistical analysis was done by repeated measure ANOVA (age, genotype, and time) or two-way ANOVA (age, genotype). n = 8–11 rat samples per group # < 0.05; ^##p < 0.01 vs. di/+.

Table I.  Comparison of various parameters of 10-day-old and adult vasopressin producing (di/+) and deficient (di/di) rats.

	10-day-old pups		Adults
	di/+	di/di	di/+	di/di
Body weight (g)	20.6 ± 0.84	17.2 ± 0.5	372.5 ± 25^++	333.9 ± 14.7^##++
Adrenal weight (mg)	4.1 ± 0.34	3.5 ± 0.25	42.0 ± 2.9	36.0 ± 1.6^##
Relative water intake (ml/kg/24 h)	n.m.	n.m.	74.9 ± 4.6	670.9 ± 36.8^##
Serum osmolality (mmol/l)	285.3 ± 1.4	336.2 ± 3.03^##	300.8 ± 2.2^++	324.8 ± 1.58^##++
Pituitary vasopressin content (ng/pituitary)	11.9 ± 0.27	0.87 ± 0.07^##	84.5 ± 9.3^++	3.6 ± 2.0^##++
Pituitary oxytocin content (ng/pituitary)	0.36 ± 0.07	0.15 ± 0.008	10.4 ± 1.4^++	7.9 ± 1.6^++

Notes: n.m., not measured. Data are expressed as mean ± SEM. Statistical analysis was done by two-way ANOVA (age, genotype); n = 10 rats per group; ^##p < 0.01 vs. di/+; ⁺⁺p < 0.01 vs. pups.

Figure 6.  CBG binding capacity in the serum of 10-day-old and adult Brattleboro rats. In pups, the vasopressin deficiency resulted in a significant increase in CBG binding capacity. In adults, CBG binding capacity was greater than in pups, with no difference between the genotypes. Data are expressed as mean ± SEM. Statistical analysis was done by two-way ANOVA (age, genotype). n = 7–8 rats per group. ^##p < 0.01 vs. di/+;⁺⁺p < 0.01 vs. pups.