Prostaglandin FP receptors do not contribute to 24-hour intraocular pressure variation in mice.

PURPOSE It is not known whether the prostaglandin FP receptor plays an important role in endogenous 24-hour regulation of intraocular pressure. The purpose of this study was to compare 24-hour intraocular pressure (IOP) in FP receptor-knockout mice with that of wild-type mice that have normal FP receptor expression. METHODS The 24-hour IOP profile was determined by rebound tonometry in FP-knockout and wild-type mice. Peak and trough IOP was then measured by microneedle cannulation of the anterior chamber in homozygous (FP(-/-); n = 8), heterozygous (FP(+/-); n = 14), and C57BL/6 background strain mice (FP(+/+); n = 11). To confirm any differences in baseline IOP between genotypes, midafternoon IOP was also measured in a larger, separate group of FP(-/-) mice (n = 20), FP(+/-) mice (n = 49), and FP(+/+) (n = 23) wild-type littermates. RESULTS Trough IOPs were measured between 10 AM and 12 PM, peak IOPs were measured between 8 and 10 PM. For FP(+/+), FP(+/-), and FP(-/-) mice trough IOP was 16.2, 15.3, and 15.1 mm Hg and peak IOPs were 18.2, 18.4, and 17.7 mm Hg, respectively. There was no significant difference among genotypes for mean peak or mean trough IOP or for peak-trough difference in IOP among genotypes (P > 0.05, ANOVA). In addition, there was no significant difference in midafternoon IOP between genotypes in a larger population (n = 92) of FP-knockout and wild-type mice. CONCLUSIONS An intact FP receptor does not appear to be critical for normal 24-hour IOP regulation in the mouse eye.