Table 1

Effect of chronic E2-17β-S or E2 administration (0.5 and 5 nmol/day for 23 days) on the plasma levels of free E2, LH, FSH, and PRL in ovariectomized female rats

Ovariectomized female Sprague Dawley rats (6.5 weeks old) were randomly divided into one control group, two E2 treatment groups, and two E2-17β-S treatment groups, with 7–8 animals/group. Each animal was surgically implanted under the back skin with an Alzet osmotic minipump (model 2004; release rate of 0.25 μl/h for up to 28 days) containing a desired concentration of E2, E2-17β-S, or vehicle only. Twenty-three days after estrogen treatment, the animals were sacrificed by decapitation, and their blood samples were collected in Vacutainer test tubes containing heparin as described in “Materials and Methods.” The plasma levels of free E2 were determined by using the double-antibody RIA kit provided by Diagnostics Products Corp., and the plasma levels of LH, FSH, and PRL were analyzed at the National Hormone and Pituitary Program by using 125I-labeled RIAs. Each value is the mean ± SE of six to eight animals.
Treatment groupsE2 (pg/ml)LH (ng/ml)FSH (ng/ml)PRL (ng/ml)
Control4.2 ± 1.618 ± 1.139 ± 2.15 ± 1.4
E2-17β-S (0.5 nmol/day)8.6 ± 0.521 ± 1.347 ± 2.94 ± 0.3
E2-17β-S (5 nmol/day)8.2 ± 0.43 ± 0.7a35 ± 1.817 ± 4.3b
E2 (0.5 nmol/day)6.8 ± 1.310 ± 1.2b48 ± 2.05 ± 0.7
E2 (5 nmol/day)10.6 ± 1.52 ± 0.7a37 ± 2.812 ± 1.8b
  • a P < 0.01 as compared to the corresponding control.

  • b P < 0.05 as compared to the corresponding control.