Ransjö M, Fredholm B B, Lerner U H
Department of Oral Pathology, University of Umeå, Sweden.
Bone Miner. 1988 Jan;3(3):225-34.
The effect on cyclic AMP levels and bone resorption by two methylxanthine cyclic AMP phosphodiesterase (PDE) inhibitors, isobutyl-methylxanthine (IBMX) and theophylline, and two non-xanthine PDE inhibitors, Ro 20-1724 and rolipram, was studied in cultured mouse calvarial bones. Cyclic AMP accumulation in calvarial bones increased when Ro 20-1724 (0.1 mmol/l) or rolipram (30 mumol/l) was present in culture medium in 2 h incubations, and when IBMX (0.3 mmol/l) or theophylline (3 mmol/l) was present in 4 h incubations. The cyclic AMP response to PDE-inhibitors could be completely abolished by the cyclooxygenase-inhibitor indomethacin (1 mumol/l). In 120 h cultures, IBMX, theophylline, Ro 20-1724 and rolipram stimulated the release of 45Ca from calvarial bones prelabelled in vivo with 45Ca. This stimulatory effect could not be seen when the endogenous production of prostaglandins was reduced by adding indomethacin (1 mumol/l), hydrocortisone (1 mumol/l) or meclofenamic acid (1 mumol/l) to culture medium. These concentrations of indomethacin, hydrocortisone and meclofenamic acid did not reduce PTH- (10 nmol/l) or choleratoxin-stimulated (0.1 micrograms/ml) 45Ca release from mouse calvarial bones cultured for 120 h. The stimulation of 45Ca release in long-term cultures by the PDE inhibitors could be demonstrated in the presence of indomethacin, provided adenylate cyclase was stimulated by forskolin (1-10 nmol/l). The stimulatory effect of 1 alpha (OH)D3 on 45Ca release could not be potentiated by the PDE-inhibitor rolipram. These results suggest that basal adenylate cyclase activity in cultured murine calvaria is very low and that therefore PDE inhibitors are inactive unless a stimulator of adenylate cyclase is present. The adenylate cyclase stimulator may be an endogenous autacoid such as a prostaglandin.
在培养的小鼠颅骨中研究了两种甲基黄嘌呤环磷酸腺苷磷酸二酯酶（PDE）抑制剂异丁基甲基黄嘌呤（IBMX）和茶碱，以及两种非黄嘌呤PDE抑制剂Ro 20-1724和咯利普兰对环磷酸腺苷水平和骨吸收的影响。当在2小时孵育的培养基中存在Ro 20-1724（0.1 mmol/l）或咯利普兰（30 μmol/l）时，以及当在4小时孵育中存在IBMX（0.3 mmol/l）或茶碱（3 mmol/l）时，颅骨中环磷酸腺苷的积累增加。环氧化酶抑制剂吲哚美辛（1 μmol/l）可完全消除对PDE抑制剂的环磷酸腺苷反应。在120小时的培养中，IBMX、茶碱、Ro 20-1724和咯利普兰刺激了预先在体内用45Ca标记的颅骨中45Ca的释放。当通过向培养基中添加吲哚美辛（1 μmol/l）、氢化可的松（1 μmol/l）或甲氯芬那酸（1 μmol/l）降低前列腺素的内源性产生时，这种刺激作用未见。这些浓度的吲哚美辛、氢化可的松和甲氯芬那酸并未降低甲状旁腺激素（10 nmol/l）或霍乱毒素刺激（0.1 μg/ml）的、从培养120小时的小鼠颅骨中释放的45Ca。只要腺苷酸环化酶受到福斯高林（1 - 10 nmol/l）的刺激，在吲哚美辛存在的情况下，PDE抑制剂对长期培养中45Ca释放的刺激作用就可以得到证明。PDE抑制剂咯利普兰不能增强1α（OH）D3对45Ca释放的刺激作用。这些结果表明，培养的小鼠颅骨中的基础腺苷酸环化酶活性非常低，因此除非存在腺苷酸环化酶刺激剂，PDE抑制剂是无活性的。腺苷酸环化酶刺激剂可能是一种内源性自分泌物质，如前列腺素。
