Endogenous porphyrins in murine skin and transplanted PAM-212 squamous cell carcinoma tissues after injection of delta-aminolevulinic acid.

After intraperitoneal (IP) injection of delta-aminolevulinic acid (ALA), the endogenous porphyrins in murine skin and tumor tissues were determined by a method involving solvent and acid extractions. The results showed that the total amount of porphyrins in the tumor tissues after ALA injection was much higher than that in the skin from the same mice, although the amount of porphyrins in the skin from the ALA-injected mice was higher than that from the saline-injected (control) mice. The porphyrins in the tumor were mostly protoporphyrin and coproporphyrin, with only a small amount of uroporphyrin. The optimum period for porphyrin accumulation in the tumor as well as in the skin was 1 hour after the injection of ALA. As the period was extended to 3 and 6 hours, the amount of porphyrins in these tissues decreased considerably. These findings could be valuable for further application of ALA in the photodynamic therapy of skin cancer.

A study on the sequence of phototoxic effects of rose bengal using retinal pigment epithelial cells in vitro.

This paper describes a study on the sequence of the phototoxic effects of rose bengal (RB), a fluorescein derivative used as a vital stain in the diagnosis of certain external ocular diseases. Bovine melanotic RPE cells were grown in culture. These cells were labeled with [51Cr] and exposed to visible light in the presence of various concentrations of RB; the leakage of [51Cr] from the cells was used as a measure of cell lysis. Exposure to light of the cells with 0.3-10 microM RB induced approximately 13 to 43% cell lysis. The lysis progressively increased when the exposure time was varied from 10 to 30 min. A relatively short period of irradiation in the presence of RB was sufficient to produce sublytic cellular injury which could subsequently lead to complete cell lysis even in the absence of the photochemical treatment. The dark reaction was time-dependent, and reached a maximum for a given irradiation period. Our results thus show that there are two different processes that could eventually lead to the cell lysis: (a) a phototoxic effect which caused a sublytic damage and (b) a dark reaction that followed.

Binding of chlorpromazine to cultured retinal pigment epithelial cells loaded with melanin.

The accumulation of chlorpromazine (CPZ) in cultured bovine amelanotic retinal pigment epithelial (RPE) cells artificially loaded with melanin was investigated. The melanin was isolated from human eye bank eyes. Suspensions of the melanin were added to the RPE cells and incubated for 3 hrs. The cells ingested the melanin which was dispersed in the cytoplasm of the cells. They were not adhering to the cell membrane. The melanin-loaded cells grew in culture, although their rate of growth was slower than that of the control RPE cells not loaded with melanin. When the melanin-loaded cells were treated with CPZ, these cells accumulated a greater amount of CPZ than the control cells. A greater amount of CPZ was released from the melanin-loaded cells than from the control cells. The results suggest that some drugs or chemicals such as CPZ could accumulate in vivo in larger quantities and for longer periods in melanotic cells than in nonmelanotic cells. These compounds may subsequently be released into the extracellular fluid, thus affecting the neighbouring cells. This phenomenon may play an important role in the activities of these drugs in the melanotic cells and in the cells adjacent to the melanotic cells. These results suggested that cultured cells loaded with melanin could be used as a suitable model for studying the mechanisms of binding of drugs to intracellular melanin, and of their subsequent release outside the cells.

Bio-effects of extremely low frequency electromagnetic fields (60 Hz.) on the healing of corneal epithelial wound: an in vitro study.

The organ cultures of standardized epithelial wound of rabbit cornea, were exposed to electric and magnetic fields components of the extremely low frequency (60 Hz) sinusoidal electromagnetic field, separately or in combination. The electric field was applied as a pure electric current via an agar-salt bridge, and the magnetic field component was applied as a pure polarized magnetic field by means of a pair of energized coils in a Helmholtz configuration. The two field components were at right angles to each other and in phase (phi = 0 degrees) when applied in combination. Their vectors or planes of polarization were parallel to the surface of the culture dish. The three exposure combinations used were: a) electric current density of 0.19 V/m (30 microA/cm2) and/or magnetic fields strength of 1.0 Gauss. (low intensity) b) electric current density of 0.31 V/m (50 microA/cm2) and/or magnetic fields strength of 1.5 Gauss. (medium intensity) c) electric current density of 0.57 V/m (90 microA/cm2) and/or magnetic fields strength of 2.5 Gauss. (high intensity). After 2 days of exposure the incorporation of radiolabelled thymidine into DNA of the regenerating epithelial cells was determined. Results showed thymidine incorporation (adjusted by regression for differences in the levels of DNA in corneal wound) (DNA*) depended upon the electromagnetic field strength. The only significant effect on this outcome, was an interaction effect between the electric (E) and magnetic (M) fields employed. The size and direction of this interaction depended strongly on the maximum field strengths. At the lowest level DNA* was significantly lower when both fields were present than would be expected from the effects of either field alone. At the highest level, DNA* was significantly higher. There were no significant effects for medium field strengths.