MODULATION OF ORNITHINE DECARBOXYLASE ACTIVITY BY PROLACTIN IN SEMINAL-VESICLES OF THE RAT

The stimulatory effect of prolactin on sexual accessory glands is well established, though the mechanism of trophic action remains poorly un derstood. We have therefore assessed the effect of high levels of prol actin on ornithine decarboxylase activity and polyamine content in sem inal vesicles (SV) of adult rats. Hyperprolactinaemia was induced by i mplantation of tissue fragments of a prolactin-secreting tumour 7315a, and the rats killed at 35 days post-inoculation. Serum levels of prol actin were increased significantly (p<0.001) in tumour-bearing rats. L evels of testosterone in serum were reduced markedly, whereas LH level s remained unchanged. SV weight in the experimental group was not sign ificantly different from that in the corresponding control group. A cl ear increase in ornithine decarboxylase activity of SV was observed (p <0.001) in the hyperprolactinaemic rats. However, there was no change in the polyamine content of SV in tumour-bearing rats, compared to the control group. These results indicate that ornithine decarboxylase ac tivity in SV of adult rats is regulated mainly by prolactin. This expe rimental model may be useful for identification of some of the events involved in the trophic action of prolactin.