L-690,330 is a competitive inhibitor of inositol monophosphatase (IMPase) with a Ki value of between 0.2 and 2 μM depending on the source of IMPase [1].
In the phosphatidylinositol (PI) cycle cell signalling pathway, IMPase is involved as a key enzyme. Inositol monophosphates, inositol(1)phosphate [Ins(l)P], inositol(3)phosphate [Ins(3)P], and inositol(4)phosphate [Ins(4)P] are hydrolyzed by IMPase and produce free inositol. Free inositol can then be used to synthesize PI [1].
In carbachol-stimulated m1 CHO cells, the treatment with L-690,330 alone did not increase the amount of [3H]InsP1. In the absence of L-690,330, the treatment with carbachol alone increased levels of [3H]InsP1, resulted in levels ranging from 20 to 100% above basal [3H]InsP1 levels. In the presence of carbachol, lithium at 10 mM increased the amount of [3H]InsP1 by approximate five folds (relative to [3H]InsP1 levels in carbachol-stimulated cells) and the EC50 value of this effect was about 1 mM. In carbachol-stimulated cells, L-690,330 at 10 mM resulted in only ~40% of the maximum response seen in the case with lithium treatment [1].
In mouse brains, in the absence of L-690,330, pilocarpine produced approximately doubled levels of Ins(1)P. In the absence of pilocarpine, L-690,330 did not affect Ins(1)P levels. Under pilocarpine-stimulated conditions, treatment with L-690,330 resulted in a pronounced accumulation of Ins(1)P, with the maximum level observed 1 h after injection. The maximum was of an approximate four-fold elevation [1].
Reference:
[1]. Atack JR, Cook SM, Watt AP, et al. In Vitro and In Vivo Inhibition of Inositol Monophosphatase by the Bisphosphonate L-690,330. Journal of neurochemistry, 1993, 60(2): 652-658.