| Popis: |
An osteoblast-like cell line (UMR 106-01 BSP), cloned from a transplantable osteosarcoma, was cultured in the presence of parathyroid hormone (PTH1-34) and metabolically labeled with [35S]sulfate, [3H]glucosamine, and [3H]tyrosine to determine proteoglycan, glycoconjugate, and protein synthesis, respectively. The synthesis of secreted proteins was substantially increased by PTH treatment. However, the synthesis of bone sialoprotein and proteoglycans was, at best, only moderately stimulated by PTH. Hyaluronan (HA) synthesis was dramatically stimulated by PTH in this cell line. A 5-6-fold increase in HA production was observed using 10(-8) M PTH, and even a 50% increase was detected using 10(-10) M PTH. The PTH-induced stimulation of HA synthesis was rapid and transient, reaching a maximum level (approximately 560 pmol of HA disaccharide equivalents/h/10(6) cells at 10(-8) M PTH) by 4-7 h after hormone exposure and returning to control levels by 12-15 h after the initial treatment. Lastly, the majority of this HA synthesis stimulated by PTH required only a short exposure (90 min) to the hormone. These data suggest (i) that normal osteoblasts (or a subpopulation of preosteoblasts) probably synthesize HA in response to PTH treatment, and (ii) that this PTH-induced synthesis of HA most likely involves some signal transduction mechanism(s). |
