Inositol trisphosphate mediates the action of hypertrehalosemic hormone on fat body of the American cockroach, Periplaneta americana
2001
Steele, J.E. | Garcha, K. | Sun, D.
The rate of synthesis of inositol trisphosphate (InsP3) in trophocytes derived from disaggregated cockroach (Periplaneta americana) fat body increases following treatment of the cells with hypertrehalosemic hormone I or II (HTH-I, -II) in vitro. Trophocytes preloaded with [3H]inositol display a significant increase in InsP3 synthesis as early as 15 s after addition of the hormone. When the trophocytes are pre-incubated with LiCl and subsequently incubated with HTH the [3H] content of the InsP3 fraction is greater than that found with HTH alone. This is taken as evidence that inositol monophosphate phosphatase is part of the mechanism for clearing InsP3 from the cytosol. In contrast to HTH, octopamine, which is also capable of exerting a hypertrehalosemic effect in the cockroach, does not increase the synthesis of InsP3. 1-Octadecyl-2-methyl-rac-glycero-3-phosphocholine (ET-18-OCH3), a potent and selective inhibitor of phosphatidylinositol phospholipase C, blocks the activation of phosphorylase by HTH-I as well as the hypertrehalosemic effect induced by the hormone.
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