Helium-Neon laser irradiation of hepatocytes can trigger increase of the mitochondrial membrane potential and can stimulate c-fos expression in a Ca2+-dependent manner.
OBJECTIVE
To gain some insight into the photostimulation of isolated hepatocytes irradiated with Helium-Neon (He-Ne) laser light certain biochemical events were studied with respect to two mechanisms: i) the direct light dependent activation of certain biochemical events investigated in intact cells and isolated mitochondria, ii) the indirect stimulation of processes per se light independent.


METHODS
Irradiation of either isolated hepatocytes or isolated rat liver mitochondria was carried out with He-Ne laser (wavelength, 632.8 nm; fluence, 0.24 J cm-2; fluence rate, 12 mW cm-2). Changes in mitochondrial membrane potential in isolated hepatocytes were monitored using the cationic probe safranine. The c-fos expression was studied by Northern blot and immunoblot analysis.


RESULTS
As a result of irradiation, increase of the mitochondrial membrane potential was found to occur in irradiated hepatocytes both in the presence or in the absence of CaCl2. The hyperpolarization of the mitochondrial membrane is assumed to cause an increase in mitochondrial Ca2+ uptake that was measured in isolated mitochondria. Finally, an increase in c-fos expression was found in irradiated hepatocytes when incubated in the presence of CaCl2.


CONCLUSIONS
This paper gives additional information on the mechanism by which He-Ne laser light, either directly or in a cascade-like effect dependent on increase in cell Ca2+, can cause cell stimulation.
Greco
M
M
Centro di Studio sui Mitocondri e Metabolismo Energetico, C.N.R., Via Amendola 165/A I-70126 BARI, Italy. csmmmg14@area.area.ba.cnr.it
Vacca
R A
RA
Moro
L
L
Perlino
E
E
Petragallo
V A
VA
Marra
E
E
Passarella
S
S
D000818:Animals; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism*; D006371:Helium; D022781:Hepatocytes / Q000378:metabolism* / Q000528:radiation effects*; D015151:Immunoblotting; D017136:Ion Transport; D007834:Lasers; D008297:Male; D008564:Membrane Potentials; D008930:Mitochondria, Liver / Q000378:metabolism* / Q000528:radiation effects*; D009356:Neon; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D015854:Up-Regulation
D016760:Proto-Oncogene Proteins c-fos; D006371:Helium; D009356:Neon; D002118:Calcium