Estrogenic Effects on Rat Lacrimal Gland Function

Abstract

 

Purpose:

 

1. Determine estrogenic effects on tear production & breakup time. 2. Determine whether the rat lacrimal gland contains progesterone/estrogen sensitive receptors and the effect of estrogen..

 

Methods:

 

24 female Sprague-Dawlet rats, aged 15 months divided into two treatment arms. 1. 12 rats received subQ placebo pellet (Intact) 2. 12 rats received subQ pellet containing 1.5 mg of 17 beta-estradiol in a 90-day release matrix (E2) Both groups received treatment until 18 months of age. Serum estrogen level was measured prior to treatment and at 18 months of age using [I¹²⁵] radioimmunoassay. Rats underwent induction with isoflurane anesthesia for 3 mins. Tear Volume Assessment: Modified Schirmer's filter paper strips placed in upper palpebral fissure for 5 mins. After 5 mins, test strips removed and tear height recorded. Tear Breakup Time: 1.0 microliter of fluorescein placed on the corneal surface followed by 3 manual blinks. Time to first break in tear film measured. Procedure was then repeated 3 times. Exenteration was performed on all 24 subjects. The orbital lacrimal gland was segmented and processed using H+E staining techniques as well as estrogen/progesterone sensitive histochemical processing.

 

Results:

 

1. Rats treated with placebo pellets had signficantly higher tear volume compared with estrogen-treated rats (one-way ANOVA with Tukey's post hoc analysis).2. Time to first breakup of tear film was significantly higher in rats treated with placebo pellets compared with those receiving estrogen (one-way ANOVA with Tukey's post hoc analysis).

 

Conclusions:

 

Estrogen supplementation leads to reduced tear volume and more rapid tear breakup time compared with age-matched controls.By using aged female rats treated with estrogen for 3 months, we created a model of keratoconjunctivitis sicca arising from hormone replacement therapy.  

 

 

Keywords: lacrimal gland • clinical laboratory testing • cornea: tears/tear film/dry eye