细胞松弛素B在细胞内同微丝的正端结合, 并引起F-肌动蛋白解聚，阻断亚基的进一步聚合。当将细胞松弛素加入到活细胞后，肌动蛋白纤维骨架消失，使动物细胞的各种活动瘫痪, 包括细胞的移动、吞噬作用、胞质分裂等。
Kd: 2.2 nM (F-actin, with Mg 2+ ), 1.4 nM (F-actin, with Mg 2+ /K + )
Cytochalasin B is a cell-permeable mycotoxin binding to the barbed end of actin filaments, inhibits the enlongation and shortening of actin filaments, with K d s of 2.2 nM and 1.4 nM for F-actin in the presence of MgCl 2 (2 mM) or MgCl 2 (2 mM) plus KCl, respectively. Cytochalasin B (0.1-10 μM) shows inhibitory effect on multiple murine cancer cell lines, with IC 50 s of 2.56 μM (M109c), 10.46 μM (B16BL6), 105.5 μM (P388/ADR), 51.9 μM (P388/S) and IC 80 s of 12.23 μM (M109c), 44.86 μM (B16BL6), 188.4 μM (P388/ADR), 84.1 μM (P388/S) after treatment for 3 h, with IC 50 s of 0.25 μM (M109c), 0.37 μM (B16F10), 0.87 μM (B16BL6), and IC 80 s of 0.75 μM (M109c), 1.21 μM (B16F10), 10.41 μM (B16BL6) after treatment for 4 days. Cytochalasin B (6 μM) increases the myofibrillar fragmentation index (MFI), which is attributed to the intensely breaking of myofibrillar proteins into short segments. Cytochalasin B also accelerates the disruption of actin filaments. In addition, Cytochalasin B accelerates the transformation from F-actin to G-actin, lowering the content of F-actin and significantly increasing G-actin bands during postmortem conditioning.
Cytochalasin B (10, 25, 50 mg/kg, i.p.) dose-dependently increases the life expectancy of Balb/c mice bearing with P388/ADR leukemias. Cytochalasin B at 50 mg/kg produces 10 % long-term survival in the multidrug resistant P388/ADR cohort, and 40 % long-term survival in the drug sensitive P388/S cohort.