Spontaneous histamine release after exposure to hyperosmolar solutions.

Since basophils from certain allergic individuals release histamine spontaneously in aqueous or deuterium oxide-containing buffers, we examined spontaneous release after a brief exposure to hyperosmolar buffers. With leukocytes from 71 normal and allergic volunteers, it was found that 15-minute suspension in 770 mosm/kg Ca++-free buffers caused the cells to release 3% to 83% of cellular histamine (mean 29 +/- 3) when the cells were resuspended in isosmolar buffers containing Ca++. The cells from individuals with a history of food allergy were significantly more easily activated when the cells were compared to cells of normal volunteers (p less than 0.005), but cells from other allergic volunteers were more readily activated as well. Activation was maximal at 770 mosm/kg and occurred in the absence of Ca++, whereas subsequent histamine release was partially Ca++ dependent. Activation could be observed as early as 30 seconds and was maximal at 15 minutes; histamine release from activated cells was almost as rapid. We conclude that the basophils from certain allergic individuals demonstrate unusual "releasability" and that this responsiveness to osmotic activation could play a role in reactions to hyperosmolar radiocontrast media.