['To study the effects of tumor necrosis factor (TNF) on the neonatal mouse osteoblast-enriched calvarial cells and effects of protein kinase C (PK C) inhibitor, 1-(5-isoquinolinesulfonyl)-2 -methylpiperazine (H-7) on the TNF actions.', '[3H]TdR uptake by the osteoblasts was used to measure cell proliferation. Cellular alkaline phosphatase (AIP) and tartrate resistant acid phosphatase (trAcP) activities were determined spectrophotometrically.', 'TNF (1-100 kU . L-1) inhibited both proliferation and expression of AIP activity, but stimulated trAcP activity. These TNF-induced actions were blocked by simultaneous addition of H-7 (5-20 mumol . L-1).'] Does protein kinase C inhibitor H-7 block effects of tumor necrosis factor on bone cells?