Tissue interaction with LASER occurs due to the presence of cellular photoacceptors that allow themselves to be stimulated just as the plant has Chlorophyll the tissue in mammals are the Chromatophores. This leads to second consideration that takes into account the optical property of the tissues. The absorption and dispersion of the light energy are dependent upon the wavelength both absorption and dispersion occurs more in the blue region than in the red region. As the tissues are more red due to the presence of Chromatophores (Hemoglobin) and the absorption and the penetration both occur more in band at wavelength shorter than 600nm this is why the red wavelength is the most healing and rejuvenating in the semiconductor LASERs group. On the other hand water another of the important component of the tissue begins to absorb the light energy in wavelengths greater than 1150nm such that the LASER is nonfunctional. This brings us to a point called the OPTICAL WINDOW, which lies between 600 and 1150nm as shown in the diagram front of the post.
Even though lights such as blue, green or yellow may have higher absorbance or penetrating values in clear fluids i.e. optically transparent, but in medium where everything is red the absorbance of low level laser is best in red and Near Infra red (NIR) light (600-950nm). (4)
Now with the knowledge obtained regarding the penetration of the Red or NIR light into the cellular matrix the LLL T does two basic functions and these are as follows:-
A) Restoration of cell morphology.
B) Stimulation of numerous secondary effects.
Restoration of cell morphology: - The NIR light acts upon the cellular respiratory chain specifically located on the mitochondrial membrane integral proteins which are as follows:-
1) NADH dehydrogenase.
2) Succinate dehydrogenase.
3) Cytochrome C reductase.
4) Cytochrome C oxidase.
5) ATP Synthetase
6) Ubiquinone and Cytochrome C (both are freely diffusible)
Studies have shown that No 4 i.e. Cytochrome C oxidase absorbs most light than the other proteins, but the main final result is the production of more ATP which eventually will allow the cell to produce more cAMP and regulate more Ca++ and thereby regulate all of the functions of the cell including genetic expression, nerve impulse transmission, muscular activity and even blood coagulation.
The production of Nitric oxide is another factor due to the constant competition with Oxygen in the cell morphology restoration
NO is known to cause vasodilation by its effect upon guanylate cyclase to form cGMP which phosphorylates the myosin in the muscles and thereby causing relaxation of the smooth muscle of the vessel walls. This only occurs in the area that can be irradiated by the NIR light thereby eliminating toxic substance accumulated there and also supplying the oxygen to other areas that have lesser amounts. The accumulation of NO is also not healthy because of the same competition with oxygen as seen in Cytochrome C oxidase.
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