Galectin-3 is a β-galactoside-binding protein implicated in diverse biological processes. We found that galectin-3 induced human monocyte migration in vitro in a dose-dependent manner, and it was chemotactic at high concentrations (1.0 μM) but chemokinetic at low concentrations (10–100 nM). Galectin-3-induced monocyte migration was inhibited by its specific mAb and was blocked by lactose and a C-terminal domain fragment of the protein, indicating that both the N-terminal and C-terminal domains of galectin-3 are involved in this activity. Pertussis toxin (PTX) almost completely blocked monocyte migration induced by high concentrations of galectin-3. Galectin-3 caused a Ca2+ influx in monocytes at high, but not low, concentrations, and both lactose and PTX inhibited this response. There was no cross-desensitization between galectin-3 and any of the monocyte-reactive chemokines examined, including monocyte chemotactic protein-1, macrophage inflammatory protein-1α, and stromal cell-derived factor-1α. Cultured human macrophages and alveolar macrophages also migrated toward galectin-3, but not monocyte chemotactic protein-1. Finally, galectin-3 was found to cause monocyte accumulation in vivo in mouse air pouches. These results indicate that galectin-3 is a novel chemoattractant for monocytes and macrophages and suggest that the effect is mediated at least in part through a PTX-sensitive (G protein-coupled) pathway.

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A radioimmunoassay method for endothelin was developed. Antisera raised against endothelin 1 showed significant crossreaction with endothelin 2 and 3 (45 and 13%, respectively). Considerable endothelin immunoreactivity was shown to be present in the cerebrospinal fluid of patients with a subarachnoid hemorrhage, ranging from 0.3 pmol/l cerebrospinal fluid to 4.5 pmol/l cerebrospinal fluid, though no endothelin immunoreactivity was observed in the cerebrospinal fluid of controls and patients with cerebral infarction, subdural haematoma or brain tumours. Endothelin immunoreactivity was also observed in two out of five cerebrospinal fluid samples from patients with cerebral bleeding. Reverse phase high performance liquid chromatography showed that the main immunoreactive component in cerebrospinal fluid appeared to elute at the same position. There was, however, an immunoreactive component which eluted at the same position as endothelin 3. These results may support the idea that endothelin immunoreactivity in the cerebrospinal fluid originate mainly from endothelial and neural tissues and that endothelin may contribute to the generation of the vasospasm often observed in subarachnoid hemorrhage, a conclusion based on the exceptionally high endothelin immunoreactivity in cerebrospinal fluid observed in patients with subarachnoid haemorrhage.