Possible involvement of protein' kinase C in parathyroid hormone degradation by osteoblast-like rat osteosarcoma cell line UMR106

The effects of 12-O-tetraadecanoyl phorbol-13-acetate (TPA). 1-oleoyl-2-acetyl-glycerol (OAG), and 1-(5-isoquinoline-sulfonyl)-2-methylpiperazine (H-7) on the parathyroid hormone (PTH) degrading activity in a PTH-responsive osteoblast-like rat osteosarcoma cell line UMR106 were investigated to assess the role of Ca 2+-activated. phospholipid dependent protein kinase (protein kinase C) on the degradation of hormones. TPA and OAG, activators of protein kinase C, enhanced the PTH degrading activity dose-dependently. Whereas H-7, an inhibitor of protein kinase C, exhibited a dose-dependent inhibition on this activity. These data suggest that protein kinase C activation may enhance PTH degrading activity by UMR106 cells as a possible regulator of PTH degradation.