ANGIOTENSIN-II EFFECTS ON THE CYTOSOLIC FREE CA-2+ CONCENTRATION IN N1E-115 NEURO-BLASTOMA CELLS - KINETIC-PROPERTIES OF THE CA-2+ TRANSIENT MEASURED IN SINGLE FURA-2-LOADED CELLS

Abstract: The effect of angiotensin II on the cytosolic free Ca2+ concentration was measured in single mouse neuroblastoma N1E‐115 cells loaded with fura‐2. Angiotensin II induced a transient concentration‐dependent increase in Ca2+ and also increased the production of inositol polyphosphates. The Ca2+ increase did not require extracellular Ca2+ and was unaffected by pretreatment with pertussis toxin. These data suggest that angiotensin II increased Ca2+ by an inositol tris‐phosphate‐mediated release of intracellular Ca2+ following activation of phospholipase C via a pertussis toxin‐insensitive guanine nucleotide binding protein. Similar results were obtained with bradykinin. The angiotensin II‐ or bradykinin‐induced increase in Ca2+ occurred after a concentration‐dependent latent period. Low concentrations of agonist elicited a small increase in Ca2+ following a variable lag that sometimes exceeded 1 min, whereas at maximally effective angiotensin II concentrations a larger, more rapid increase in Ca2+ occurred without a measurable delay. In some cells, oscillatory increases in Ca2+ were induced by angiotensin II and bradykinin. Possible mechanisms to explain the concentration dependency of the latent period and the oscillatory nature of the increases of Ca2+ are discussed. These results indicate that the mouse neuroblastoma N1E‐115 cell represents a useful model for studying the signal response transduction mechanisms regulating the effects of angiotensin II in neuronal cells. Copyright © 1990, Wiley Blackwell. All rights reserved