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 (11,4,5P(3)) in kidney and bone cells. I t has been reported the 11,4,5P, increases calcium uptake by brain syn aptosomes. Because PTH also augments calcium entry in brain synaptosom es, it is possible that PTH induces the generation of 11,4,5P(3) in th ese 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) increa sed the IP3 production (35 +/- 52%). The results indicate that PTH act ivates the phosphoinositol turnover in brain synaptosomes and that thi s pathway may be involved in the PTH-induced increase in [Ca2+](i) in brain synaptosomes. (C) 1995 by the National Kidney Foundation, Inc.