March 2012
Volume 53, Issue 14
ARVO Annual Meeting Abstract  |   March 2012
Vitreous Humor Buffering Capacity Of Rabbit, Bovine, And Porcine
Author Affiliations & Notes
  • Mohannad Shawer
    Bausch and Lomb, Rochester, New York
  • Martin J. Coffey
    Bausch and Lomb, Rochester, New York
  • Eric Phillips
    Bausch and Lomb, Rochester, New York
  • Footnotes
    Commercial Relationships  Mohannad Shawer, Bausch and Lomb (E); Martin J. Coffey, Bausch and Lomb (E); Eric Phillips, Bausch and Lomb (E)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 463. doi:
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      Mohannad Shawer, Martin J. Coffey, Eric Phillips; Vitreous Humor Buffering Capacity Of Rabbit, Bovine, And Porcine. Invest. Ophthalmol. Vis. Sci. 2012;53(14):463.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : To compare the vitreous buffering capacity of three species: rabbit, bovine, and porcine. This study examines the ability of the vitreous to accommodate formulations with wide ranges of pH and its effect on the local and whole vitreous pH, and clarity of the vitreous as result of such changes in its pH.

Methods: : The vitreous from three species (bovine, porcine, and rabbit) were used for pH titration. For each measurement, a 5-mL sample of vitreous was placed in a scintillation vial and stirred. After the initial pH stabilization, the pH was recorded and aliquots of either 0.1M HCl or 0.1M NaOH were added every minute for 30 minutes. Prior to the performing the titrations, vitreous samples were equilibrated with a 5% CO2 in air mixture and the pH was adjusted to 6.5 - 7.5. Equilibration with the 5% CO2 in air mixture was maintained during the HCl titrations, but not during the NaOH titrations because doing so was found to artificially increase the observed buffer capacity as the CO2 solubility increased at higher pH. Vitreous clarity was evaluated by optical density measurements at low pH after incubation with HCl aliquots for 20 minutes.

Results: : Although the titration curves for the three species had some notable differences, all three species exhibited similar buffering capacity toward both acidic and basic titration. Titration toward both acidic and basic sides (over about 3 pH units) showed a buffer capacity of 6.3-8 mmol L-1 pH-1. Using published information about the composition of the vitreous in various species, we can identify which vitreous components are contributing to the observed buffer capacity. The clarity of the vitreous was found to diminish at low pH. The vitreous maintained its clarity at pH 3 and 2, but significant turbidity was observed at pH 1.

Conclusions: : All three animal species are predicted to react similarly with regard to vitreous pH when injected with a non-neutral pH formulation. The observed buffer capacity for the vitreous in all three species examined here is in good agreement with what would be predicted based on published information on the vitreous composition.

Keywords: vitreous • injection • pH regulation/protons 

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