Thyroidectomy modulates rat prostatic monosaccharides

Earlier studies have shown that thyroid hormones play an important role in glycoprotein metabolism in the prostate. In this paper, hypothyroidism indu ced changes in prostatic glycoprotein-associated monosaccharides and fructo se concentrations were studied in 30-day-old peripubertal rats. Hypothyroid ism was induced by total surgical thyroidectomy and confirmed by radioimmun oassay (RIA) of thyroid hormones and thyroid stimulating hormone (TSH). Ani mals were killed after 30 and 60 days post-thyroidectomy. To test the direc t effect of thyroid hormones on prostatic monosaccharides, prostatic tissue was incubated for 24 h at 37 degrees C with 25, 50 or 100 ng/mL T-3. Ventr al prostatic hexosamines and sialic acid concentrations were significantly decreased in hypothyroid rats aged 30 and 60 days, whereas fucose concentra tion was increased at 30 days but decreased at 60 days in hypothyroid rats. In the case of the dorsolateral prostate, hypothyroidism enhanced the conc entration of hexosamines but caused a decrease in levels of fucose, sialic acid and fructose, irrespective of the duration of hypothyroidism. Concentr ations of fucose, fructose and hexosamines in the anterior prostate were de creased and sialic acid concentration was increased in 60-day hypothyroid r ats. In in vitro studies, the concentrations of fucose, sialic acid and hex osamines were significantly increased in all three prostatic lobes irrespec tive of the T-3 dose with which they had been incubated. A consistent incre ase in fructose concentration was observed in anterior and dorsolateral pro states when incubated with different doses of T-3 stimulation. It is conclu ded that the influence of hypothyroidism on prostatic monosaccharides seems to be specific for each sugar in different lobes of the prostate. These re sults clearly show that thyroid hormones differentially regulate prostatic glycoprotein metabolism.