Spontaneous histamine secretion during isolation of rat cardiac mast cells

To test the hypothesis that spontaneous release of histamine occurring during an isolation protocol may modify responses of rat cardiac mast cells (connective tissue-type mast cells) to secretagogues. We assessed two protocols for enzymatic dispersion utilizing collagenase, hyaluronidase, and deoxyribonuclease; with protease (Protocol 1, n = 8) or without protease (Protocol 2, n = 3). Spontaneous release of histamine was quantified following mechanical and enzymatic dispersion of the whole heart. Total histamine loss (Mean +/- SEM) was 963+/-92 and 833+/-60 ng/g of tissue weight following Protocols 1 and 2. Percentages of histamine release from cell isolates following Protocol 1 were 40+/-5%, 41+/-6%, and 51+/-7% at 0, 30, and 300 microg/mL of compound 48/80. Enzymatic dispersion of cardiac mast cells affects their response to secretagogues.