Enhanced Ca handling in thioglycolate-elicited peritoneal macrophages.

In macrophage biology, resident peritoneal macrophages (RPMs) and thioglycolate-elicited peritoneal macrophages (TGPMs) have been traditionally utilized as primary cultured models. RPMs and TGPMs exhibit distinct morphological, functional and metabolic characteristics, although it remains unclear how cellular Ca handling differs between them. In our Fura-2 Ca imaging, TGPMs displayed elevated resting Ca levels, increased store Ca contents and facilitated store-operated Ca entry (SOCE) compared with RPMs. The intensified intracellular Ca stores were enriched with major luminal Ca-binding proteins inducibly expressed in TGPMs. The elevated resting Ca level was predominantly maintained by constitutive Ca influx, probably through the transient receptor potential (TRP) family members TRPP2, TRPM7 and TRPA1. These TRP family channels seemed to be largely activated in a manner dependent on phospholipase C activity, and together with Orai channels, contributed to SOCE. Moreover, Ca-dependent K channels efficiently facilitated SOCE by enhancing the Ca driving force in TGPMs. The consolidated cellular Ca handling described may underlie the specialized cell-physiological features of TGPMs, such as vital proliferation, active migration and avid phagocytosis.