Parathyroid hormone stimulates the generation of inositol 1,4,5-triphosphate in brain synaptosomes

Parathyroid hormone (PTH) increases the levels of the second messenger, inositol 1,4,5 triphosphate (I1,4,5P3) in kidney and bone cells. It has been reported the I1,4,5P3 increases calcium uptake by brain synaptosomes. Because PTH also augments calcium entry in brain synaptosomes, it is possible that PTH induces the generation of I1,4,5P3 in these structures as well. The current study examined the effect of PTH-(1-84) on myoinositol turnover in vitro in rat brain synaptosomes. PTH-(1-84) in concentration of 10(-6)mol/L significantly (P < 0.01) increased the IP3 production (35 +/- 52%). The results indicate that PTH activates the phosphoinositol turnover in brain synaptosomes and that this pathway may be involved in the PTH-induced increase in [Ca2+]i in brain synaptosomes.