Assessment of proliferative activity of glandular cells in hyperfunctioning parathyroid gland using flow cytometric and immunohistochemical methods.

The proliferative activity of epithelial cells in hyperfunctioning parathyroid glands was estimated by flow cytometric and immunohistochemical procedures. A total of 30 parathyroid glands, 29 hyperfunctioning glands, and 1 normal gland were studied. The pathology of the 29 glands was determined to be hyperplasia in 19 and adenoma in 10. The S-phase cell population was expressed in terms of the S-phase fraction (%SPF) calculated from the histogram by DNA flow cytometry and in terms of the BrdU immunostaining labeling index (BrdU LI). Cells in all stages of the cell cycle were studied by Ki-67 immunostaining and expressed in terms of the labeling index (Ki-67 LI). Both BrdU LI and Ki-67 LI values were low, ranging from 0% to 0.58% and from 0.21% to 2.62%, respectively. The BrdU LIs were lower than the Ki-67 LIs, ranging from one-sixth to one-twelfth of the values depending on the disease. There were significant correlations between the two indices (p < 0.001). The %SPF determined by flow cytometry was consistently higher than both the BrdU LI and the Ki-67 LI. This discrepancy cannot be explained precisely, and further improvements are required for the flow cytometric analysis of %SPF. The cell cycle study by BrdU and Ki-67 immunohistochemistry suggested that the glandular cells of the hyperfunctioning parathyroid were characterized by low proliferative activity. No evidence of rapid cell turnover rate assumed from the flow cytometric study could be observed in the hyperfunctioning parathyroid gland.