AgNORs in estrogen-induced and lisuride- and thyreoidin-inhibited rat anterior pituitary hyperplasia. Computer image analysis and nonautomated AgNOR typing.

OBJECTIVE: A model of estrogen (E)-induced rat anterior pituitary hyperplasia blocked partly by thyroid hormones (estradiol plus thyreoidin [ET]) and nearly completely by lisuride (estradiol plus lisuride [EL]) and thyreoidin plus lisuride combination (estradiol plus thyreoidin plus lisuride [ETL]) was used to test a computer image analysis program, LUCIA, for argyrophilic nucleolar organizer region (AgNOR) evaluation.

STUDY DESIGN: Nuclear and AgNOR area were measured in more than 700 cells in each experimental group. The nucleoli were also typed without the automated procedure.

RESULTS: Mean nuclear area was significantly higher in E and lower in T. In all groups with blocked hyperplasia (ET, EL, ETL) the mean nuclear area was lower than in T. Mean AgNOR area was significantly higher in E but also, to a lesser extent, in T. The ET combination produced a partly diminished mean AgNOR area as compared to E; a severe reduction was observed in the EL and ETL groups. In nucleolar typing, thyreoidin, lisuride and their combination inhibited the increase in large nucleoli with finely dispersed AgNORs induced by estradiol.

CONCLUSION: The LUCIA image analysis program for AgNOR evaluation proved able to monitor the slight changes in AgNORs in thyroid hormones- and lisuride-inhibited, estradiol-induced rat anterior pitutary hyperplasia.