Sáez JC, Moreno AP, Spray DC. Nor epinephrine induces Ca 2+ release from intracellular stores in rat pinealocytes. J. Pineal Res. 1994: 16: 57–64. In rat pinealocytes, an increase in intracellular Ca2+ concentration ([Ca2+]i) due to Ca2+ influx in response to nor epinephrine (NE) is a well recognized event involved in regulating several metabolic functions. Since NE also stimulates the metabolism of phosphatidyl inositols in rat pineal gland, it is conceivable that Ca2+ release from intracellular stores also contributes to the NE‐induced increase in [Ca2+]i. In this communication, we report that in rat pinealocytes loaded with fura‐2, a Ca2+ indicator, NE induced a transient increase in [Ca2+]i that preceded the known Ca2+ influx. This novel [Ca2+]i response to NE was detected in pinealocytes bathed with Ca2+‐free saline and prevented by TMB‐8, a blocker of Ca2+ release from intracellular stores, supporting the notion that the transient NE‐induced Ca2+ response was due to Ca2+ release from intracellular stores. In addition, after an extended exposure to NE a new addition of this neurotransmitter did not elicit the phasic Ca2+ response, and application of increasing amounts of NE induced a Ca2+ response that was progressively smaller, suggesting desensitization. Thus, NE is proposed to increase [Ca2+]i in rat pinealocytes by two mechanisms: (1) phasic release from intracellular stores and (2) tonic influx through a mechanism activated by larger applications of NE than required to evoke the phasic release.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Pineal Research|
|State||Published - Mar 1994|
- Key words: intracellular Ca—neurotransmitterα‐adrenoceptors—desensitization—fura‐2— TMB‐8
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