concentrations. Baseline values are presented with range. Total production of proges- terone and cortisol after ACTH administration was calculated from the area under each
ŽŽ .
. respective curve according to the formula: R s Ý T q T
r2 300 min, where i s 0,
i iq30
30 . . . 300 min. The duration of significantly increased plasma hormone concentrations was determined in relation to individual baseline levels. Comparison of the mean group
data concerning total hormone production and duration of significantly increased plasma Ž
w
hormone concentrations was done by a Student’s t-test using Minitab Minitab Release
. 10.2, Minitab, PA, USA .
In accordance with the lower detection limit of the assays, cortisol concentrations were fixed at 5.5 nmol l
y1
and progesterone concentrations at 0.1 nmol l
y1
. The concentrations of cortisol and progesterone in the baseline samples were transformed to
Ž .
logarithms in base 10 and differences between groups tested by a repeated measures analysis of variance for effect of group, time and group-time interaction using the
Ž MIXED procedure of the statistical analysis systems package SAS Institute, Cary, NC,
. USA, 1996 . Least-square means were obtained for combination of effects and were
compared using Student’s t-test. Correlations between cortisol and progesterone concentrations were calculated for
baseline samples and after treatment, respectively. Results are presented as mean SEM. Differences P - 0.05 were considered signifi-
cant.
3. Results
3.1. Baseline concentrations Fig. 1 In many cases, progesterone baseline concentrations were below the detection limit
Ž .
and did not differ between the groups P s 0.25 . In RBH, the mean level was
y1
Ž
y1
.
y1
Ž 0.1 0.03 nmol l
, range: 0.1–0.5 nmol l , and in VH, 0.2 0.02 nmol l
range:
y1
. Ž
. 0.1–0.4 nmol l
. RBH had a significantly higher P - 0.01 mean baseline concentra-
y1
Ž
y1
. tion of cortisol with a mean of 10.1 2.3 nmol l
range: 5.5–54 nmol l compared
y1
Ž
y1
. with 2.6 0.2 nmol l
in VH range: 2–6 nmol l . For neither hormone was there
any difference over time and no interaction between group of animals and time. One of the RBH had a considerably higher cortisol baseline concentration than the
rest of the RBH. She showed consistently nervous and aggressive behaviour during day 1 of the trial. Without her values, the RBH cortisol mean baseline concentration would
y1
Ž
y1
. have been 6.2 4.29 nmol l
range: 5.5–17 nmol l , which is still significantly
Ž .
higher P - 0.001 than the mean for VH. Since her baseline progesterone concentration did not differ significantly from the rest of the group, it was included in the baseline
calculation.
3.2. Posttreatment concentrations Fig. 2 Within 30 min after the ACTH-treatment, all animals had a significant and highly
Ž .
correlated RBH: r s 0.84, VH: r s 0.82 rise in both cortisol and progesterone. RBH
R. Bage
et al.
r Animal
Reproduction
Science 63
2000 65
– 76
˚
70
Ž .
Ž .
Fig. 1. Control: mean plasma concentrations and SDs of cortisol upper panel and progesterone lower panel in ovariectomised VH, ns 5 and RBH, ns 5 after Ž
. Ž
. NaCl administration control . NaCl was injected after the third blood sample arrows . Blood samples were collected every 30 min for 6 h.
R. Bage
et al.
r Animal
Reproduction
Science 63
2000 65
– 76
˚
71 Ž
. Ž
. Fig. 2. ACTH-challenge: mean plasma concentrations and SDs of cortisol upper panel and progesterone lower panel in ovariectomised VH, ns 5 and RBH, ns 5
Ž .
after ACTH administration. ACTH was injected after the third blood sample arrows . Blood samples were collected every 30 min for 6 h.
Ž .
had a significantly greater P - 0.001 cortisol response than VH, most prominent
Ž .
Ž P s 0.06 in the peak values within an hour after the treatment samples no. 4 and 5; 30
. and 60 min after the ACTH injection, respectively . Progesterone levels after treatment
Ž .
did not differ P s 0.45 between the groups, although it was complementary to the
release of cortisol. Compared with VH, RBH had a higher peak in cortisol but a smaller rise in progesterone.
The duration of significantly elevated hormone concentrations after treatment did not differ between the groups. In RBH as a group, progesterone concentration was elevated
Ž .
for 204 min range: 150–300 min
and the VH group returned to pretreatment Ž
. Ž .
progesterone level after 246 min range: 180–300 min , P s 0.30 . Cortisol concentra- Ž
. tions were elevated for a longer period, with a mean of 276 min range: 240–300 min
Ž .
Ž .
in RBH and 240 min range: 210–300 min in VH P s 0.08 .
4. Discussion
