Histamine: its metabolism and localization in mammary gland

1. Mammary gland of mouse (Mus musculus), rat (Rattus rattus), guinea pig (Cavia porcellus), cow (Bos taurus) and pig (Sus scrofa) contains different but always high concentrations of histamine. 2. Generally, the tissue histamine is localized in mast cells, although non-mast cell histamine immunoreactivity is also present in mammary glands of the mouse, cow and pig. No histamine immunoreactive nerves could be detected. 3. Mammary glands are able to synthesize and inactivate histamine; the activity of specific histidine decarboxylase and at least one of the catabolizing enzyme could be demonstrated. 4. Histamine fulfils basic criteria for being involved in physiological function of mammary glands.