Determination of epidermal proliferative activity in experimental mouse tail test by AgNOR analysis

Nucleolar organizer regions are segments of DNA coding ribosomal genes, which can be histologically detected by silver technique as so-called AgNORs. The estimation of AgNOR number and AgNOR size are currently under investigation as markers of cellular proliferation activity. We therefore examined the epidermal AgNOR expression after topical application of different antiproliferative compounds using the mouse tail test. The epidermis of 0.025% fluocinolone acetonide-treated mouse tails had the lowest AgNOR expression. Pretreatment with 0.2% Anthralin, 1% propyl gallate and 2% 3,4-hexaalkylbenzoylacrylic acid, an experimental phospholipase-A2 inhibitor, also revealed significant inhibition effects of epidermal AgNOR expression. Native and petrolatum-treated epidermis as control showed the highest AgNOR expression. The AgNOR results in basal cells proved to be more informative than these in the stratum spinosum, the best parameter was the AgNOR number. The obtained results were closely related to the values of the corresponding studies of PCNA expression. The AgNOR method seems to be useful for estimation of antiproliferative efficiency of pharmacological substances. This technique is simple in handling and can be applied using paraffin-embedded tissue sections.