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 induced changes in prostatic glycoprotein-associated monosaccharides and fructose concentrations were studied in 30-day-old peripubertal rats. Hypothyroidism was induced by total surgical thyroidectomy and confirmed by radioimmunoassay (RIA) of thyroid hormones and thyroid stimulating hormone (TSH). Animals were killed after 30 and 60 days post-thyroidectomy. To test the direct 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 T3. Ventral prostatic hexosamines and sialic acid concentrations were significantly decreased in hypothyroid rats aged 30 and 60 days, whereas fucose concentration was increased at 30 days but decreased at 60 days in hypothyroid rats. In the case of the dorsolateral prostate, hypothyroidism enhanced the concentration of hexosamines but caused a decrease in levels of fucose, sialic acid and fructose, irrespective of the duration of hypothyroidism. Concentrations of fucose, fructose and hexosamines in the anterior prostate were decreased and sialic acid concentration was increased in 60-day hypothyroid rats. In in vitro studies, the concentrations of fucose, sialic acid and hexosamines were significantly increased in all three prostatic lobes irrespective of the T3 dose with which they had been incubated. A consistent increase in fructose concentration was observed in anterior and dorsolateral prostates when incubated with different doses of T3 stimulation. It is concluded that the influence of hypothyroidism on prostatic monosaccharides seems to be specific for each sugar in different lobes of the prostate. These results clearly show that thyroid hormones differentially regulate prostatic glycoprotein metabolism.