Decrease in the AgNOR number in Dunning R3327 prostate cancers after treatment with an agonist and antagonist of luteinizing hormone-releasing hormone.

The argyrophilic staining of the nucleolar organizer region (AgNOR) in cells of Dunning R3327 rat prostate tumors was studied and the effect of hormonal treatments on their appearance was analyzed. The nuclei of the control tumor cells contained 4.1 +/- 0.17 AgNOR granules. Treatment of rats for 8 weeks with luteinizing hormone-releasing hormone (LH-RH) agonist (D-Trp-6-LH-RH) and antagonist SB-75 induced a marked inhibition of tumor growth and decreased significantly (P less than 0.01) the number of Ag-NORs in the tumors to 2.89 +/- 0.10 AgNOR granules/cell in the group given the agonist and to 2.82 +/- 0.10 after therapy with the highest dose of the antagonist. A reduced AgNOR number (3.14 +/- 0.16) also was found after 3 days of treatment with SB-75 (P less than 0.05), but the AgNORs returned to near control values 1 week after the short-term therapy, showing the reversibility of these changes. These results suggest that the AgNOR method, which was widely tested on human tumors in the past few years, can be a valuable technique in experimental tumor pathology and useful in the evaluation of the effects of various treatments.