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The ocular pulse decreases aqueous humor outflow resistance by stimulating nitric oxide production.

Publication ,  Journal Article
Madekurozwa, M; Stamer, WD; Reina-Torres, E; Sherwood, JM; Overby, DR
Published in: American journal of physiology. Cell physiology
April 2021

Intraocular pressure (IOP) is not static, but rather oscillates by 2-3 mmHg because of cardiac pulsations in ocular blood volume known as the ocular pulse. The ocular pulse induces pulsatile shear stress in Schlemm's canal (SC). We hypothesize that the ocular pulse modulates outflow facility by stimulating shear-induced nitric oxide (NO) production by SC cells. We confirmed that living mice exhibit an ocular pulse with a peak-to-peak (pk-pk) amplitude of 0.5 mmHg under anesthesia. Using iPerfusion, we measured outflow facility (flow/pressure) during alternating periods of steady or pulsatile IOP in both eyes of 16 cadaveric C57BL/6J mice (13-14 weeks). Eyes were retained in situ, with an applied mean pressure of 8 mmHg and 1.0 mmHg pk-pk pressure amplitude at 10 Hz to mimic the murine heart rate. One eye of each cadaver was perfused with 100 µM L-NAME to inhibit NO synthase, whereas the contralateral eye was perfused with vehicle. During the pulsatile period in the vehicle-treated eye, outflow facility increased by 16 [12, 20] % (P < 0.001) relative to the facility measured during the preceding and subsequent steady periods. This effect was partly inhibited by L-NAME, where pressure pulsations increased outflow facility by 8% [4, 12] (P < 0.001). Thus, the ocular pulse causes an immediate increase in outflow facility in mice, with roughly one-half of the facility increase attributable to NO production. These studies reveal a dynamic component to outflow function that responds instantly to the ocular pulse and may be important for outflow regulation and IOP homeostasis.

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Published In

American journal of physiology. Cell physiology

DOI

EISSN

1522-1563

ISSN

0363-6143

Publication Date

April 2021

Volume

320

Issue

4

Start / End Page

C652 / C665

Related Subject Headings

  • Time Factors
  • Stress, Mechanical
  • Physiology
  • Perfusion
  • Nitric Oxide
  • Models, Biological
  • Mice, Inbred C57BL
  • Mice
  • Mechanotransduction, Cellular
  • Male
 

Citation

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Madekurozwa, M., Stamer, W. D., Reina-Torres, E., Sherwood, J. M., & Overby, D. R. (2021). The ocular pulse decreases aqueous humor outflow resistance by stimulating nitric oxide production. American Journal of Physiology. Cell Physiology, 320(4), C652–C665. https://doi.org/10.1152/ajpcell.00473.2020
Madekurozwa, Michael, W Daniel Stamer, Ester Reina-Torres, Joseph M. Sherwood, and Darryl R. Overby. “The ocular pulse decreases aqueous humor outflow resistance by stimulating nitric oxide production.American Journal of Physiology. Cell Physiology 320, no. 4 (April 2021): C652–65. https://doi.org/10.1152/ajpcell.00473.2020.
Madekurozwa M, Stamer WD, Reina-Torres E, Sherwood JM, Overby DR. The ocular pulse decreases aqueous humor outflow resistance by stimulating nitric oxide production. American journal of physiology Cell physiology. 2021 Apr;320(4):C652–65.
Madekurozwa, Michael, et al. “The ocular pulse decreases aqueous humor outflow resistance by stimulating nitric oxide production.American Journal of Physiology. Cell Physiology, vol. 320, no. 4, Apr. 2021, pp. C652–65. Epmc, doi:10.1152/ajpcell.00473.2020.
Madekurozwa M, Stamer WD, Reina-Torres E, Sherwood JM, Overby DR. The ocular pulse decreases aqueous humor outflow resistance by stimulating nitric oxide production. American journal of physiology Cell physiology. 2021 Apr;320(4):C652–C665.

Published In

American journal of physiology. Cell physiology

DOI

EISSN

1522-1563

ISSN

0363-6143

Publication Date

April 2021

Volume

320

Issue

4

Start / End Page

C652 / C665

Related Subject Headings

  • Time Factors
  • Stress, Mechanical
  • Physiology
  • Perfusion
  • Nitric Oxide
  • Models, Biological
  • Mice, Inbred C57BL
  • Mice
  • Mechanotransduction, Cellular
  • Male