Scandinavian society for the study of diabetes Abstracts Seventh Meeting

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46039/1/125_2005_Article_BF01219478.pd

Dissociation between changes in cytoplasmic free Ca2+ concentration and insulin secretion as evidenced from measurements in mouse single pancreatic islets.

Simultaneous measurements of cytosolic free Ca2+ concentration and insulin release, in mouse single pancreatic islets, revealed a direct correlation only initially after stimulation with glucose or K+. Later, there is an apparent dissociation between these two parameters, with translocation of alpha and epsilon isoenzymes of protein kinase C to membranes and simultaneous desensitization of insulin release in response to glucose. Recovery of insulin release, without any concomitant changes in cytosolic free Ca2+ concentration, after addition of phorbol 12-myristate 13-acetate, okadaic acid, and forskolin supports the notion that the desensitization process is accounted for by dephosphorylation of key regulatory sites of the insulin exocytotic machinery

Regulation of intracellular Ca2+ in response to muscarinic and glutamate receptor agonists during the differentiation of NTERA2 human embryonal carcinoma cells into neurons

Single cell microfluorimetry was used to study intracellular calcium ion signals (Ca2+i) evoked by acetylcholine (ACh), glutamate receptor agonists and by KCl-induced membrane depolarization, during neuronal differentiation of the human embryonal carcinoma (EC) cell line, NTERA2. In undifferentiated NTERA2 EC cells, Ca2+i was elevated in response to ACh, but not to the glutamate receptor agonists NMDA, kainate or AMPA. The ACh-induced rise in Ca2+i was dependent upon both Ca2+ influx and Ca2+ mobilization from cytoplasmic calcium stores. Three other human EC cell lines responded similarly to ACh but not to glutamate for KCl-induced depolarization. In neurons derived from NTERA2 cells by retinoic acid induction, Ca2+i signals were evoked by ACh, NMDA, kainate and by an elevation of the extracellular KCl concentration. As in ur (differentiated EC cells, the ACh-mediated increases in Ca2+i were governed by both Ca2+ influx and Ca2+ mobilization. In contrast, the effects of NMDA, kainate and KCl did not involve intracellular Ca2+ mobilization. The appearance of glutamate and KCl responsiveness was not detected in non-neuronal differentiated derivatives of NTERA2 cells. Using a number of pharmacologically defined muscarinic receptor antagonists we found that NTERA2 EC cells express M1, M3, M4 and possibly M5 receptor subtypes linked to changes in Ca2+i, whilst only M3 and M5 are present in NTERA2-derived neurons. The results were supported by PCR analysis of the muscarinic mRNA species expressed in the cells. The data demonstrate that differentiation of NTERA2 EC cells into neurons involves the induction of functional glutamate receptors coupled to rises in Ca2+i, find changes in the expression of muscarinic ACh receptor subtypes. © European Neurosci ence Association