Effects of plant-induced hypervitaminosis D on cutaneous structure, cell differentiation and cell proliferation in cattle.

Solanum glaucophyllum (Sg) (synonym S. malacoxylon) is a plant toxic to cattle due to its high levels of 1,25-dihydroxyvitamin D3 as glycoside derivatives. Sg causes a disease characterized by wasting and calcification of soft tissues. The effects of vitamin D are not only important in calcium homeostasis, but also in immune regulation, cell growth and cell differentiation. Skin samples in Sg-intoxicated and control heifers were studied histologically. Cellular differentiation and proliferation were analysed by immunohistochemical expression of cytokeratins, involucrin and proliferating cell nuclear antigen (PCNA). The results were obtained by image processing and analysis and were statistically evaluated. Sg-intoxicated cattle showed atrophy of epidermis and severe involution of hair follicles and of sebaceous and sweat glands. As judged by PCNA expression, cellular proliferation was reduced, even though the reduction was not statistically significant. The analysed markers of differentiation, e.g. involucrin and cytokeratins 10 and 11, changed in relation to Sg-poisoning. The possible pathogenesis of the skin lesions is discussed.