Developmental patterns of histamine-like immunoreactivity in the mouse

We studied the appearance and distribution of histamine (HA) during mouse embryogenesis, neonatal period, and adulthood using a specific rabbit HA antiserum and indirect immunofluorescence. HA first appeared on the Embryonic Day 13 (E13) in scattered mast cells in the gastrointestinal (GI) muscularis externa and liver. The splenic primordium contained a dense population of intensely HA-immunoreactive (HA-ir) cells from E13 on. From E15 to the birth, HA was detected in many embryonic cell types. On E15, the first HA-ir epithelial endocrine cells appeared in the oxyntic mucosa. In addition to the HA-ir cells in GI tract and liver, some nerve cells in ganglia of the peripheral nervous system (PNS), some fibers in spinal and cranial nerves, nerve fibers in mesenterium, and nerve plexuses of the gastrointestinal muscularis externa were HA-ir from E15 on. Occasional HA-ir nerve fibers were detected within the glandular epithelium of the oxyntic mucosa, pancreas, and salivary glands during late embryogenesis. During the same period, bright fluorescence was observed in cells of the kidney convoluted tubules and pancreatic islet cells. From E14 on, mast cells exhibiting bright fluorescence were scattered throughout the connective tissue of the fetus, and their number increased rapidly with age. Their density was especially high in subcutaneous connective tissue. Embryonic epidermal cells showed faint HA immunoreactivity. In musculoskeletal tissues, developing bone and occasional striated muscle cells exhibited HA immunoreactivity. Interestingly, most cells in liver showed transiently weak HA immunoreactivity during embryogenesis. In adult mouse, HA was stored only by scattered mast cells, oxyntic epithelial cells, and neurons in the tuberomamillary nucleus of the brain. The other HA-containing embryonic cells were negative for HA in adult mouse. In conclusion, HA immunoreactivity is widely distributed in epithelial, neuronal, and mast cells in various organs during mouse embryogenesis.