title: Regulation of intracellular calcium in dispersed fat body trophocytes of the cockroach, Periplaneta americana, by hypertrehalosemic hormone.
abstract: Incubation of trophocytes from dissaggregated fat body of Periplaneta americana with either of the hypertrehalosemic hormones, HTH-I or HTH-II, leads to an increase in the cytosolic concentration of Ca(2+) from approximately 80 to approximately 310nM with a rise time of approximately 110s. The Ca(2+) concentration then declines to the resting level during the ensuing 5min. In the absence of extracellular Ca(2+) the increase in [Ca(2+)](i) due to HTH is limited to approximately 100nM. The calmodulin inhibitors calmidazolium and W-7 also limit to a similar degree the ability of HTH to increase [Ca(2+)](i). Phorbol 12-myristate 13-acetate, an activator of protein kinase C, was shown to block Ca(2+) entry through the plasma membrane. Additional evidence to support the view that HTH enhances Ca(2+) influx has been obtained by measuring the quenching of fura-2 fluorescence when Ca(2+) is replaced with Mn(2+).
authors.affiliation: Department of Zoology, The University of Western Ontario, Ont., N6A 5B7, London, Canada
authors.forename: D
authors.initials: D
authors.lastname: Sun
authors.forename: J E.
authors.initials: JE
authors.lastname: Steele