The role of mast cells in redistribution of tele-methylhistamine in the body.

The basis of this study was the assumption that mast cells can take up tele-methylhistamine (MeHi), as is known for other biogenic amines. The influence of extracellular MeHi on its uptake (active or passive) in isolated rat mast cells and in different rat tissues was studied in vitro. Rat peritoneal mast cells were incubated for 15 or 30 min at 37 or 1 degree C with different concentrations of MeHi. Submandibular gland, skeletal muscle, lung and heart of the rat (200-500 mg of each) were chopped and incubated for 20 min at 37 or 1 degrees C in buffer containing MeHi. Histamine (Hi) and MeHi in the cells and in the tissues were then determined by HPLC assay. Mast cells were capable of taking up MeHi in a time- and dose-dependent manner. MeHi levels increased from 5-10 ng per ml of incubated cell suspension (control) to 60-100 ng/ml after 15 min incubation. It can be assumed that the accumulation of MeHi in mast cells is due to a simple diffusion process since no significant change was noticed at 1 degree C. The preincubation of the cells with serotonin reduced MeHi accumulation, thus indicating MeHi competes with the same binding sites in mast cells as Hi and serotonin. Tissues showed high capacity for MeHi accumulation and MeHi surmounted endogenous Hi levels. Uptake was reduced at 1 degree C, yet the accumulation of MeHi was still high. The results indicate that mast cells can take up a smaller portion of free MeHi and they can have a function in its micro-regulation whereas other tissue cells have a predominant role in the removal of free MeHi from the blood.