Influence of hemithyroidectomy on bromodeoxyuridine incorporation into DNA of rat thyroid follicular cells.

OBJECTIVE

To examine the bromodeoxyuridine (BrdU) incorporation into DNA of thyroid follicular cells (TFC) in the remaining thyroid lobe after hemithyroidectomy (hemiTx) in 1, 2, 3 and 4 weeks time after surgery.

METHODS

The experiment was performed on male Wistar rats. The Cell Proliferation Kit (Amersham, UK) was used in order to detect the incorporated BrdU. The BrdU incorporation was expressed as a BrdU labeling index (BrdULI; a number of BrdU-immunopositive TFC per 1000 TFC).

RESULTS

1. No statistically significant changes of BrdULI were observed between the particular groups of sham-operated (shamTx)-rats in 1, 2, 3 and 4 weeks time after surgery, and in comparison of each of them to the controls (at time "0"); 2. In the first 2-week period after hemiTx, an increasing effect of that surgical procedure on BrdULI value was observed (the highest BrdULI value was detected 2 weeks after hemiTx); 3. In the third and fourth week after hemiTx, a decrease of BrdULI value was observed, as compared to BrdULI groups (in 1- and 2-week time after hemiTx), and to the controls (at time "0"); 4. An increase of weight of contralateral lobe was shown in 1, 2, 3 and 4 weeks after hemiTx in comparison to thyroid lobe weight in intact rats.

CONCLUSIONS

During the first 2 weeks after hemiTx, the thyroid growth in the remaining thyroid lobe seems to ensue by hyperplasia mechanisms. The thyroid growth processes during subsequent 2 weeks (3rd and 4th) could result from other mechanisms - for example, from hypertrophy.