Effect of chain length of aliphatic amines on histamine potentiation and release.

Diamines in the series NH(2).(CH(2))(n).NH(2) specifically potentiate histamine contractions of the guinea-pig ileum and inhibit the enzymatic destruction of histamine. These activities are greatest with short-chain compounds (n approximately 5). Diamines also release histamine from isolated tissues and depress the contractility of plain muscle and the motility of paramecia. These activities increase with chain-length and are probably limited only by solubility. The parallelism between histamine-releasing activity and toxicity also extends to the monoamines in the series CH(3).(CH(2))(n-1).NH(2). Histamine-releasing activity of both series increases with increase of pH and can mainly be attributed to the non-ionized base.From the results on the effect of chain-length and ionization on activity, it is suggested that aliphatic amines release histamine by penetration of the cell membrane in the non-ionized form, followed by exchange in the ionic form with intracellular histamine.