The influence of genetic background on conventional outflow facility in mice.
OBJECTIVE
Intraocular pressure (IOP) varies between genetically distinct strains of mice. The purpose was to test the hypothesis that strain-dependent differences in IOP are attributable to differences in conventional outflow facility (C).


METHODS
The IOP was measured by rebound tonometry in conscious or anesthetized BALB/cJ, C57BL/6J, and CBA/J mice (N = 6-10 per strain). Conventional outflow facility was measured by ex vivo perfusion of enucleated eyes (N = 9-10 per strain).


RESULTS
Conscious IOP varied between strains, being highest in CBA/J (14.5 ± 0.9 mm Hg, mean ± SD), intermediate in C57BL/6J (12.3 ± 1.0 mm Hg), and lowest in BALB/cJ (10.6 ± 1.8 mm Hg) mice. Anesthesia reduced IOP and eliminated any detectable differences between strains. Conventional outflow facility also varied between strains, but, in contrast to IOP, C was lowest in CBA/J (0.0113 ± 0.0031 μL/min/mm Hg) and highest in BALB/cJ (0.0164 ± 0.0059 μL/min/mm Hg). Like IOP, C was intermediate in C57BL/6J (0.0147 ± 0.0029 μL/min/mm Hg). There was a strong correlation between conscious IOP and outflow resistance (1/C) from individual eyes across all three strains, revealing that 70% of the variation in IOP was attributable to variation in outflow resistance.


CONCLUSIONS
Differences in IOP among three genetically distinct murine strains are attributable largely to differences in conventional outflow facility. These results motivate further studies using mice to identify the morphologic and genetic factors that underlie IOP regulation within the conventional outflow pathway.
Department of Bioengineering, Imperial College London, London, United Kingdom.
Alexandra
A
Boussommier-Calleja
Darryl R
DR
Overby
D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism*; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation / Q000502:physiology*; D007429:Intraocular Pressure / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D014065:Tonometry, Ocular; D014129:Trabecular Meshwork / Q000378:metabolism*
intraocular pressure; mouse model; outflow facility; trabecular meshwork