Drug-induced changes in histamine and tele-methylhistamine levels in mouse peripheral tissues

To clarify the histamine (HA) dynamics in peripheral tissues, effects of drugs on the tissue HA and tele-methylhistamine (t-MH) levels were studied in mice. alpha-Fluoromethylhistidine (50 mg/kg, i.p.) significantly decreased the HA level in the stomach, but not in the liver, heart, ileum, submandibular gland and skin of mice. This compound had no significant effect on the t-MH level in any tissue examined. In non-fasted and 24-hr fasted animals, the t-MH level in the liver, heart and ileum was significantly increased by treatment with aminoguanidine (10 mg/kg, i.p.) plus pargyline (65 mg/kg, i.p.). However, in mice fasted for 48 hr, this treatment was ineffective in increasing the t-MH level in the heart and ileum, suggesting that the t-MH level in some peripheral tissues is under the influence of the food intake. Even if HA is synthetized and then metabolized in the peripheral tissues, the size of the HA pool with a rapid turnover in each tissue except for the gastric tissue seems to be very small.