The effects of glucose (16.7 mM), potassium (50 mM), forskolin (20 microM), dibutyryl cyclic AMP (1 mM) and arachidonic acid (82 microM) upon insulin release and cytosolic free calcium concentrations ([Ca2+]i) were investigated in normal rat pancreatic islets. Potassium, forskolin and dibutyryl cyclic AMP significantly raised [Ca2+]i, but elicited only minimal insulin release. In the absence of extracellular Ca2+, glucose evoked insulin release, but failed to augment [Ca2+]i. Arachidonic acid increased [Ca2+]i both in Ca-depleted and -repleted medium, but promoted insulin release only in Ca2+-repleted environment. These new observations clearly demonstrate by direct measurements that although [Ca2+]i is an important factor in exocytotic insulin release, its effect is subject to amplification or antagonism.

Animals↗

PubMedDate not supplied

Electron microprobe analysis of Ca, P, and Mg in mandibular bone.

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Animals↗

PubMedDate not supplied

Electron probe microanalysis of cementum and underlying dentin in young permanent teeth.

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Adolescent↗