Purpose: To test potential participation of pericytes in the regulation of capillary blood flow according to metabolic needs, we determined the effects when the ambient carbon dioxide (CO2) level was changed. Methods: Pericytes were isolated from capillaries of bovine retinas. Change in pHi was monitored with the fluorescent dye BCECF, and change in the contractile tone by measuring the length of wrinkles induced on a silicone surface. Results: (1) When pCO2 in the medium was raised above the physiological level (from 5% to 10% and 20%), the medium became acidified, the intracellular pH (pHi) of pericytes decreased, and the pericytes relaxed in a dose-dependent manner. When pCO2 in the medium was made lower than the physiological level (to 0% or 2%), the medium became alkalized, the pHi of pericytes gradually increased, and the pericytes contracted if they had been pre-relaxed with sodium nitroprusside (3 × 10-6 M). (2) In additional experiments, the extracellular pH (pHo) was kept at 7.4 by adjusting the ratio of NaHCO3 and NaCl in the medium as pCO2 was changed to 2%, 10% or 20%. When pCO2 was 0, HEPES buffer was used instead of the bicarbonate buffer. Under these conditions, both elevating and lowering the pCO2 caused intracellular acidification and relaxation of the cells. Conclusions: The effect of CO2 on the pHi and the contractility of pericytes is partially mediated by its influence on the pHo. Under the conditions likely to exist in living tissue (cells in mid-relaxed state, pHo affected by pCO2), elevation of CO2 causes pericytes to relax, while dispersion of CO2 causes pericytes to contract. Therefore, CO2 may contribute to the regulation of local blood flow through the contractile properties of pericytes.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience