Spectrofluorometric analysis of phylloerythrin in plasma and skin from sheep suffering from hepatogenous photosensitization.

Abstract

The increase in phylloerythrin concentration in the plasma and skin of sheep dosed with sporidesmin was studied. Sporidesmin is a mycotoxin which is known to cause liver damage resulting in phylloerythrin retention and photosensitization. Fifteen Romney × Polled Dorset lambs were divided into two groups; treatment lambs (n=11) were dosed with 0.25 mg sporidesmin per kg body weight. Both the control (undosed; n=4) and treatment lambs were kept in open pens and were exposed to natural sunlight; however, after the onset of photosensitization, the lambs were housed indoors in darkened conditions. The sporidesmin used in this study was derived from cultures of Pithomyces chartarum. The first 2 cases of photosensitization in lambs exposed to sunlight occurred 10 days post-sporidesmin dosing. Eight of 11 sporidesmin-dosed lambs became photosensitized during the entire experimental period. The spectrum of fluorescence of plasma specimens from photosensitized sheep was very similar to that obtained from plasma of healthy lambs to which phylloerythrin was added. The emission spectrum of the plasma from healthy lambs with no phylloerythrin showed minor fluorescence at 670 nm. Plasma from photosensitized lambs exhibited strong phylloerythrin-like fluorescence, having identical spectra and with a maximum of two main fluorescence bands at 649±1 nm and 709±1 nm and excitation maximum at 422 nm. Concentration of phylloerythrin in photosensitized sheep was estimated to be from 0.3 to 0.8 µmol/litre, at the day they became clinically photosensitized. Fluorescence in the skin showed similar spectra as in plasma. All lambs had a fluorescence signal with a maximum at 670 nm at the beginning of the experiment. Changes to the phylloerythrin-like spectra occurred in the skin 2 to 3 days after the plasma, and these occurred only in lambs that showed photosensitization early in the experiment. The excitation maximum of the phylloerythrin-like spectrum was at 421 nm, and this gave rise to 3 fluorescence emission peaks at 650, 670 and 710 nm.