EFFECT OF LITHIUM ON INCORPORATION OF BROMODEOXYURIDINE AND TRITIATED-THYMIDINE INTO HUMAN PARATHYROID CELLS

Objective: To measure lithium chloride-stimulated incorporation of tri tiated thymidine (H-3-TdR) and bromodeoxyuridine (BrdU) by human parat hyroid cells as an indicator of lithium's growth-promoting properties. Design: Cell suspensions derived from abnormal human parathyroid tiss ue were incubated for 5 days with graded concentrations of lithium and pulsed with either 0.074 MBq of H-3-TdR or 0.6 mug of BrdU. The H-3-T dR incorporation was measured by counting cell filtrates in a beta cou nter, and nuclear BrdU incorporation was determined by counting nuclei positively stained by an antibody to BrdU. Counts of BrdU-positive ce lls by two observers unaware of incubation conditions were correlated with H-3-TdR counts. Results: Cell suspensions derived from adenomatou s and hyperplastic parathyroid glands demonstrated a dose-related incr ease in H-3-TdR incorporation. There was close correlation between the two observers' counts of BrdU-positive cells (r=0.70, P=.01) and betw een each observer's counts and H-3-TdR counts (r=0.70, P=.02, and r=0. 90, P=.01, respectively). Conclusions: Lithium stimulates in vitro inc orporation of H-3-TdR and BrdU by abnormal human parathyroid cells, co nsistent with a growth-promoting effect.