The effect of barium on [3H]noradrenalin release from the human neuroblastoma SH-SY5Y

Chronic treatment with nicotine or potassium attenuates depolarisation-evoked noradrenaline release from the human neuroblastoma SH-SY5Y

Chronic treatment, of SH-SY5Y cells, with KCl (20 mM) for 4 days decreased 100 mM KCl-evoked noradrenaline (NA) release by 50% and nicotine (100 microM)-evoked NA release by 55%. Pretreatment with the L-type calcium channel antagonist, nifedipine, prevented this inhibitory effect of chronic exposure to 20 mM KCl on NA release. In contrast pretreatment with 10 microM nicotine for 4 days had no effect on 100 mM KCl -evoked secretion and decreased nicotinic -evoked NA release by only 25%. Inclusion of nifedipine prevented the inhibition of NA release by chronic nicotine treatment. These data are discussed in relation to effects of chronic moderate, depolarisation by either K(+) or nicotine on influx of Ca(2+) via L-type voltage sensitive calcium channels.

INAA of trace elements in colorectal cancer patients

The concentration of trace elements in samples of both colorectal cancer tumors and normal tissues of a Mexican population were irradiated for 30 s and 4 h and their elemental content were measured by instrumental neutron activation analysis. Ca, Cu, Co, I, Mg, Se, Fe, Zn, Hg, Ba, and Cr were analyzed. Alterations in Co, Fe, I, and Ba were found in tumors with respect to normal tissues.

The regulation of neurotransmitter secretion by protein kinase C

The effect of protein kinase C (PKC) on the release of neurotransmitters from a number preparations, including sympathetic nerve endings, brain slices, synaptosomes, and neuronally derived cell lines, is considered. A comparison is drawn between effects of activation of PKC on neurotransmitter release from small synaptic vesicles and large dense-cored vesicles. The enhancement of neurotransmitter release is discussed in relation to the effect of PKC on: 1. Rearrangement of the F-actin-based cytoskeleton, including the possible role of MARCKS in this process, to allow access of large dense-cored vesicles to release sites on the plasma membrane. 2. Phosphorylation of key components in the SNAP/SNARE complex associated with the docking and fusion of vesicles at site of secretion. 3. Ion channel activity, particularly Ca2+ channels.

Ca2+ entry following store depletion in SH-SY5Y neuroblastoma cells

Ca2+ entry following Ca2+ store depletion was examined in the human neuroblastoma cell line, SH-SY5Y, by measuring the concentration of intracellular free Ca2+ ([Ca2+]i) with fura-2. Application of the muscarinic agonist oxotremorine-M (oxo-M) caused an increase in [Ca2+]i. This consisted of a peak, mediated by release of Ca2+ from internal stores followed by a sustained plateau, mediated by Ca2+ entry across the plasma membrane. The Ca2+ entry resulted from depletion of intracellular Ca2+ stores This pathway was further characterized in the presence of thapsigargin, an inhibitor of the Ca2+ ATPase involved in replenishing IP3-sensitive stores. Stores were first depleted with oxo-M and thapsigargin in the absence of extracellular Ca2+. After washout of oxo-M, subsequent exposure to Ca2+ evoked reproducible increases in [Ca2+]i. Application of oxo-M plus Ca2+ had little effect on the increases in [Ca2+]i, indicating that in SH-SY5Y cells, agonist-dependent pathways contribute little to Ca2+ entry following store depletion. Mn2+, Sr2+ and Ba2+ were permeable through this pathway. Mn2+ and Ba2+ also showed slight permeability in the absence of store depletion. Ca2+ entry following store depletion was blocked by La3+ (IC50 = 75 nM) and by SKF 96365. La3+ blocked Mn2+ entry through the pathway activated by store depletion but did not affect basal Mn2+ permeability. These results indicate that SH-SY5Y neuroblastoma cells have an agonist-independent Ca2+ entry pathway activated by store depletion.