Effect of lithium on incorporation of bromodeoxyuridine and tritiated thymidine into human parathyroid cells

A. Saxe and G. Gibson
Department of Surgery, Sinai Hospital, Detroit, Mich.

OBJECTIVE: To measure lithium chloride-stimulated incorporation of tritiated thymidine (3H-TdR) and bromodeoxyuridine (BrdU) by human parathyroid cells as an indicator of lithium's growth-promoting properties. DESIGN: Cell suspensions derived from abnormal human parathyroid tissue were incubated for 5 days with graded concentrations of lithium and pulsed with either 0.074 MBq of 3H-TdR or 0.6 microgram of BrdU. The 3H-TdR incorporation was measured by counting cell filtrates in a beta counter, and nuclear BrdU incorporation was determined by counting nuclei positively stained by an antibody to BrdU. Counts of BrdU-positive cells by two observers unaware of incubation conditions were correlated with 3H-TdR counts. RESULTS: Cell suspensions derived from adenomatous and hyperplastic parathyroid glands demonstrated a dose-related increase in 3H-TdR incorporation. There was close correlation between the two observers' counts of BrdU-positive cells (r = 0.70, P = .01) and between each observer's counts and 3H-TdR counts (r = 0.70, P = .02, and r = 0.90, P = .01, respectively). CONCLUSIONS: Lithium stimulates in vitro incorporation of 3H-TdR and BrdU by abnormal human parathyroid cells, consistent with a growth-promoting effect.