Evidence of mast-cell histamine being mitogenic in intact tissue

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Abstract
We have reported previously that secretion by connective tissue mast cells (MCs) causes mitogenesis in adjacent cells in diverse rat tissues. In cultured rat mesentery there was a spontaneous release of about 45% of the histamine in 2 days, and a spontaneous marked increase in basal proliferation of the mesentery. The MC secretagogues, compound 48/80 and polymyxin B, released additional histamine and stimulated mitogenesis further. In contrast, 48/80 added to cultures of guinea-pig mesentery, the MC of which are unresponsive to the drug, did not affect the basal proliferation. However, exogenous histamine at 10−10 M mitogenically stimulated the cultured guinea-pig mesentery. A histmaine H2-receptor antagonist, which itself was mitogenically inert, significantly suppressed the 48/80-induced MC-mediated mitogenesis in rat mesenteryin vivo andin vitro. On the other hand, a histamine H1-receptor antagonist did not affect this MC-mediated mitogenesis in rat. Our findings indicate that histamine is one of possibly several mitogens which are released or activated by the secreting MC.