Protein kinase C activity affects glucose-induced oscillations in cytoplasmic free Ca²⁺ in the pancreatic B-cell

Acute stimulation of protein kinase C (PKC) inhibited glucose-induced slow oscillations in cytoplasmic free Ca²⁺-concentration, [Ca²⁺]_i, in mouse pancreatic B-cells. In PKC-depleted cells glucose induced rapid transients in [Ca²⁺]_i, lasting for approximately 10 s, superimposed on the slow oscillations in [Ca²⁺]_i. It was demonstrated that the transients did not occur in the absence of extracellular Ca²⁺. Each transient typically was preceded by a slow increase in [Ca²⁺]_i, representing the rising phase of an ordinary glucose-induced slow oscillation, and the [Ca²⁺]_i, immediately after a transient was lower than just before the spike. These data further emphasize the interplay between voltage-dependent Ca²⁺-channels and the phospholipase C system in the regulation of B-cell [Ca²⁺]_i-oscillations.