Pre-blockade of the sarco-endoplasmic reticulum (ER) calcium ATPase (SERCA) with irreversible thapsigargin depresses exocytosis in adrenal bovine chromaffin cells (BCCs). Distinct expression of voltage-dependent Ca²⁺-channel subtypes and of the Ca²⁺-induced Ca²⁺ release (CICR) mechanism in BCCs versus mouse chromaffin cells (MCCs) has been described. We present a parallel study on the effects of the acute SERCA blockade with reversible cyclopizonic acid (CPA), to repeated pulsing with acetylcholine (ACh) at short (15 s) and long intervals (60 s) at 37 °C, allowing the monitoring of the initial size of a ready-release vesicle pool (RRP) and its depletion and recovery in subsequent stimuli. We found (i) strong depression of exocytosis upon ACh pulsing at 15-s intervals and slower depression at 60-s intervals in both cell types; (ii) facilitation of exocytosis upon acute SERCA inhibition, with back to depression upon CPA washout in MCCs; (iii) blockade of exocytosis upon acute SERCA inhibition and pronounced rebound of exocytosis upon CPA washout in BCCs; (iv) basal [Ca²⁺]_c elevation upon stimulation with ACh at short intervals (but not at long intervals) in both cell types; and (v) augmentation of basal [Ca²⁺]_c and inhibition of peak [Ca²⁺]_c amplitude upon CPA treatment in both cell types, with milder effects upon stimulation at 60-s intervals. These results are compatible with the view that while in MCCs the uptake of Ca²⁺ via SERCA contributes to the mitigation of physiological ACh triggered secretion, in BCCs the uptake of Ca²⁺ into the ER facilitates such responses likely potentiating a Ca²⁺-induced Ca²⁺ release mechanism. These drastic differences in the regulation of ACh-triggered secretion at 37 °C may help to understand different patterns of the regulation of exocytosis by the circulation of Ca²⁺ at a functional ER Ca²⁺ store.

用不可逆毒胡萝卜素预阻断肌内质网 (ER) 钙 ATP 酶 (SERCA) 可抑制肾上腺牛嗜铬细胞 (BCC) 的胞吐作用。电压依赖性 Ca ²⁺通道亚型和 Ca ²⁺诱导的 Ca ^{2+ 的}不同表达已经描述了 BCC 与小鼠嗜铬细胞 (MCC) 中的释放 (CICR) 机制。我们提出了一项平行研究，研究了可逆性环哌酮酸 (CPA) 的急性 SERCA 阻断对在 37°C 下以短 (15 秒) 和长间隔 (60 秒) 重复脉冲使用乙酰胆碱 (ACh) 的影响，从而允许监测准备释放囊泡池 (RRP) 的初始大小及其在后续刺激中的消耗和恢复。我们发现 (i) 在两种细胞类型中，ACh 以 15 秒的间隔脉冲发出强烈的胞吐抑制，以及以 60 秒的间隔较慢的抑制；(ii) 在急性 SERCA 抑制时促进胞吐作用，在 MCC 中 CPA 洗脱后恢复抑制；(iii) 急性 SERCA 抑制后胞吐作用的阻断和 BCC 中 CPA 洗脱后胞吐作用的明显反弹；(iv) 基础 [Ca ²⁺] _c在两种细胞类型中以短间隔（但不是长间隔）用 ACh 刺激后升高；(v)在两种细胞类型中，CPA 处理后基础 [Ca ²⁺ ] _{c 的增加}和峰值 [Ca ²⁺ ] _c振幅的抑制，对以 60 秒间隔进行刺激的影响较温和。这些结果与以下观点一致，即在 MCC 中，通过 SERCA摄取 Ca ²⁺有助于减轻生理性 ACh 触发的分泌，而在 BCC 中，Ca ²⁺摄取到 ER 促进了这种反应，可能会增强 Ca ²⁺ -诱导Ca ²⁺释放机制。在 37 °C 时 ACh 触发的分泌调节的这些巨大差异可能有助于了解通过功能性内质网 Ca ²⁺储存中的 Ca ²⁺循环调节胞吐作用的不同模式。