Miniature swine model of phototoxicity testing.
OBJECTIVE
This study determined the threshold doses for 'solar erythema' and for phototoxic responses to 8-methoxypsoralen (8-MOP) in white skin Hanford and grey skin Yucatan miniature swine.


METHODS
For threshold erythema determinations, the UVR exposures included both UVA (315-400 nm) and UVB (290-315 nm) radiation by positioning one fluorescent 'sunlamp' among 10 'PUVA' lamps. With this configuration the UVR exposures ranged from 0.5-2.8 times the 'instrumental MED' (MEDi) for Hanford and from 1.0-5.6 times the MEDi for Yucatan. For phototoxicity determinations (i.e., with and without topically-applied graduated concentrations of 8-MOP), the UVB component was minimized by extinguishing the sunlamp, thus permitting higher UVA exposures.


RESULTS
The Hanford had the lower UV erythema dose threshold (1.0-1.4 times the MEDi) and the erythema that developed was readily observable. The exposure doses for the phototoxicity test were 5 J/cm(2) of UVA in 35 minutes or 10 J/cm(2) in 70 minutes. The phototoxic (vascular) response to 8-MOP was observed in the two highest concentrations (0.01% and 0.1%) in Hanford pigs, in a dose-related manner. Microscopic evidence of a dose-related response was also observed as the concentration of 8-MOP increased.


CONCLUSIONS
This verified that the Hanford miniature swine is the preferable strain for phototoxic effects. In contrast, UVR exposure of the Yucatan pig skin produced tanning rather than erythema, confirming that the Yucatan is the more appropriate strain for studying the melanization response. Thus, Hanford and Yucatan miniature swine have cutaneous photobiological responses that reflect their respective strain differences.
Sinclair Research Center, LLC, Auxvasse, MO 35231-1012, USA.
Heinz
H
Leigh
Paul Donald
PD
Forbes
Charles
C
Lawson
Dae Young
DY
Kim
David
D
White
Larry D
LD
Brown
Dean R
DR
Wehmeier
Jason
J
Liu
Guy F
GF
Bouchard
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004353:Drug Evaluation, Preclinical; D004890:Erythema / Q000139:chemically induced* / Q000473:pathology*; D005260:Female; D006801:Humans; D008730:Methoxsalen / Q000009:adverse effects* / Q000494:pharmacology; D017319:Photosensitizing Agents / Q000009:adverse effects* / Q000494:pharmacology; D013552:Swine; D013556:Swine, Miniature; D014466:Ultraviolet Rays / Q000009:adverse effects*
D017319:Photosensitizing Agents; D008730:Methoxsalen