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Calcium is essential in the fusion of mouse alveolar macrophages induced by 1α, 25‐dihydroxyvitamin D 3
Author(s) -
Jin Cheng He,
Segawa Akishisa,
Miyaura Chisato,
Tanaka Hirofumi,
Abe Ersuko,
Suda Tatsuo
Publication year - 1988
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041370113
Subject(s) - calcium , chemistry , incubation , fusion , biochemistry , microbiology and biotechnology , biology , philosophy , linguistics , organic chemistry
We have reported that the active form of vitamin D 3 , 1α, 25‐dihydroxyvitamin D 3 [1α, 25(OH) 2 D 3 ], directly induces activation and fusion of mouse alveolar macrophages (Abe et al., 1983, 1984). The activated state appeared to be a prerequisite to the fusion of macrophages. Macrophages began to fuse 36 hr after adding 1α, 25(OH) 2 D 3 ; the fusion rate attained a maximum of 70–80% at 72 hr. During the course of further investigating the mechanisms of fusion induced by the vitamin, we found that the calcium ion is closely involved in the fusion process of macrophages induced by 1α, 25(OH) 2 D 3 . When alveolar macrophages were cultured with 1α, 25(OH) 2 D 3 in medium with graded concentrations (0.13–1.85 mM) of calcium, the fusion rate went down in parallel with the decrease of medium calcium. Neither calcium ionophore A23187 nor 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) induced fusion of freshly isolated macrophages, but the two compounds greatly promoted fusion of the macrophages pretreated for 18 hr with 1α, 25(OH) 2 D 3 . The vitamin effect for the first 18 hr was similar, irrespective of the medium calcium concentration. In contrast, millimolar amounts of calcium were essential in the subsequent period of incubation(18–72 hr) for inducing fusion. The activation of macrophages measured by the induction of cytotoxicity and the enhancement of glucose consumption by 1α,25(OH) 2 D 3 occurred similarly, irrespective of the medium calcium concentration. These results clearly indicate that the fusion process of alveolar macrophages induced by 1α, 25(OH) 2 D 3 can be divided into two phases: (1) the calcium‐independent priming phase (0–18 hr) and (2) the calcium‐dependent progression phase (18–72 hr). 1α,25(OH) 2 D 3 is necessary only in the priming phase; A23187 and TPA can be substituted for 1α,25(OH) 2 D 3 in the progression phase.