Uterotrophic Assay of Percutaneous Lavender Oil in Immature Female Rats

Abstract

The estrogenic potential of lavender oil was evaluated in a percutaneous uterotrophic bioassay in immature female rats. Four groups of 10 immature female rats each were randomly selected on postpartum day (PPD) 16. During the 3-day treatment period (PPDs 19-21), the immature rats were separated from the dams, caged in groups of 5 in a litter box for 6 hours, and administered the vehicle control article (corn oil) or lavender oil at 20 or 100 mg/kg per day. All dosages were administered as a 5 mL/kg volume in a Hilltop Chamber (25 mm diameter; absorbent material removed) placed on the shaved back of each immature rat, and secured with micropore tape and Vetrap. A positive control group was gavaged twice daily with 2.5 μg/kg per day of 17α-ethinyl estradiol. Daily observations included viability, clinical signs, body weights, and body weight gains. All rats were euthanized 24 hours after the third and final treatment, the uteri and ovaries were removed, and the paired ovaries and wet and blotted uterine weights were recorded. No unscheduled deaths occurred. No skin reactions were observed. Both dosages of lavender oil significantly reduced body weight gains after the third day of treatment, but terminal body weights and mean absolute and relative uterine weights did not differ significantly from vehicle control values. Positive controls showed significant increases in body weight and increased mean absolute and relative uterine weights as expected. Based on these data, lavender oil, at dosages of 20 or 100 mg/kg, was not active in the rat uterotrophic assay and gave no evidence of estrogenic activity.

Lavender Products Associated With Premature Thelarche and Prepubertal Gynecomastia: Case Reports and Endocrine-Disrupting Chemical Activities

“…In one study, the comparative positive control used gavage of 17a ethynyl estradiol (44). The treatment schemes were quite different between the two groups, although it would have been a directly testable exposure with a fully accepted target end point if found positive (44). On the other hand, in our cases, the patients' suspected area of exposure, which was the breast area, was in direct contact with the essential oil and not at a distant site.…”

“…Previous studies have demonstrated that dermal exposure to essential oils results in circulating concentrations that are comparable to the concentrations used in vitro (42,43). In contrast, an industry-supported experimental study reported percutaneous exposure of LO showed no uterotropic estrogenic activity (44). An additional report indicated no estrogenic activity in a yeast assay using Lin (45).…”

“…The primary method to test uterine estrogenic activity is principally done either by ingestion or injection. In one study, the comparative positive control used gavage of 17a ethynyl estradiol (44). The treatment schemes were quite different between the two groups, although it would have been a directly testable exposure with a fully accepted target end point if found positive (44).…”

Soy Isoflavone Protects Myocardial Ischemia/Reperfusion Injury through Increasing Endothelial Nitric Oxide Synthase and Decreasing Oxidative Stress in Ovariectomized Rats

“…Rats with SI (90 mg/kg·d and 270 mg/kg·d) or E 2 (50 μ g/kg·d) administration show significant reduction in body weight. Uterine weight, used as a bioassay for estrogens [ 22 ], was measured after 4-week treatment ( Table 1 ). Uterus of lighter weight and lower concentration of E 2 were present after ovariectomy, which suggested that ovariectomy elicited estradiol deficiency and uterine atrophy ( Table 1 ).…”

Association of Early Pubertal Onset in Female Rats with Inhalation of Lavender Oil

“…A previous animal study reported that percutaneous injection of LO when performing uterotrophic assays on immature rats results in signi cantly reduced body weight gain after 3 days compared with that in the control group and a group administered 17α-ethinyl estradiol (19). However, the authors only assessed weight gain and organ-weight-to-terminal-body-weight to evaluate the presence of an estrogenic effect, and did not compared hormone levels or VO timing.…”