Topical prostaglandin F-2 alpha treatment reduces collagen types I, III, and IV in the monkey uveoscleral outflow pathway

Background: Topical prostaglandin Fz, isopropyl ester increases uveoscleral outflow in monkeys and humans. Objective: To investigate the effects of prostaglandin Fz, isopropyl ester with topical administration on collagen types I, III, and IV within the ant erior segment tissue of monkey eyes. Methods: Eight eyes of 4 cynomolgus monkeys were evaluated. One eye of each monkey was treated with 2 pg of prostaglandin Fz, isopropyl ester twice da ily for 5 days, and intraocular pressure reduction was confirmed. These eye s were fixed in methacarn, and paraffin sections were immunostained using a ntibodies to collagen types I, III, or IV. To measure staining intensity, o ptical density (OD) was determined using 2-dimensional imaging densitometry . Mean OD scores along line segments placed over the ciliary muscle were de termined. Results: Mean +/-SD OD scores for collagen types I, III, and IV were less i n the ciliary muscle of prostaglandin-treated eyes than in vehicle-treated eyes by 52% +/- 7%, 45% +/- 6%, and 45% +/- 5%, respectively. In the sclera adjacent to the ciliary body, mean OD scores for collagen types I and III were less in prostaglandin-treated eyes, by 43% +/- 32% and 45% +/- 13%, re spectively. The scleral stroma was minimally immunoreactive for collagen ty pe IV. All differences were significant by the paired Student t test (P < . 05). Conclusions: This study shows reduced collagen types I, III, and IV immunor eactivity in the ciliary muscle and adjacent sclera following topical prost aglandin Fz, isopropyl ester treatment. These reductions may contribute to the increased uveoscleral outflow observed with topical prostaglandin treat ment.