ease in i was Tipifarnib However significantly higher than the plateau increase obtained by 2 min LA stimulation, with a maximal amplitude of increase in i as 277643 nM. The strong and long-lasting increase was recovered slowly for more than 10 min after removal of LA. The mean i change during 3.5 min from start of LA stimulation was not significantly different between 2 min LA stimulation and 10 min LA stimulation. The mean Ca2+ change in the following 10 min from 3.5 min time point was significantly smaller in 2 min LA stimulation than in 10 min 18362028 LA stimulation. These data indicate a difference between acute activation of receptor and relatively long-term action of FFAs metabolism once they have come into b-cells. The mean i changes during above mentioned two time periods were calculated as the average Ca2+ levels subtracting the basal levels for the first phase increase in i and the second phase increase in i. These parameters were used in the following results and discussion sections, when the increase in i was analyzed in details. 2. Membrane Receptor-signaling Pathway and Intracellular-metabolite Signaling Pathway In order to observe the effect of FFA receptor-only-mediated signaling, GW9508 was applied to cause activation of FFA receptors without metabolites in rat b-cells. GW9508 stimulated the transient peak increase in i followed by a minor plateau increase in i, highly identical to that of 2 min LA stimulation. This result suggests that the FFA receptor-mediated increase in i should be mainly composed of the transient peak increase with minor plateau increase in i whileas the strong and long-lasting increase in i caused by 10 min LA stimulation may not be mediated by FFA receptor but LA metabolites in b-cells. Acylation of FFAs is the first step for FFA metabolism, which is achieved by Acyl-CoA synthetase. Triacsin C, the ACS inhibitor, was used to study the effects of LA metabolites on the increase in i in b-cells. Triacsin C itself did not influence i in b-cells during 20 
min incubation. After triacsin C treatment of b-cells for 5 min, 10 min LA treatment induced the transient peak increase in i while the strong and long-lasting second phase increase in i was significantly suppressed. The mean i change in the first phase 4 LA Increases i in Beta-Cells increase was not significantly different between the control and Triacsin C-treated group. The mean i change in strong and long-lasting second phase increase was significantly reduced in 10 min LA stimulation by triacsin C pre-treatment. It is suggested that FFA receptor GPR40 in b-cells is coupled to phospholipase C and Inositol triphosphate signaling pathways. In the present study, we also observed that inhibition of PLC by U73122 blocked the transient first phase increase in i, but did not influence the strong and long-lasting second phase increase in i induced by 10 min LA stimulation. The mean i change in 11121575 the first phase increase was almost fully eliminated by U73122; whereas the mean i change in the second phase was not changed by U73122. U73122 itself did not significantly influence i in b-cells. Etomoxir is the carnitine palmitoyltransferase 1 inhibitor and inhibits the transportation of long-chain acyl-CoA into mitochondria for b-oxidation. However, etomoxir did not influence the first or second phase increase in i induced by 10 min LA stimulation. Etomoxir itself did not significantly influence i in b-cells. 3. The Contribution of Extracellular Calcium and Intracellular Calcium