Intraglandular colloid induced nuclear proliferation of murine thymic cells as determined by flow cytometry.

The ability of intraglandular colloid, the holocrine secretion of cells of the marginal half of the bovine pituitary intermediate lobe, to enhance or suppress the proliferation of immature thymic cells of CH3/6JH mice, 4 to 6 weeks of age, was studied. The mice were given subcutaneous injections of colloid for 3 consecutive days at a dose of 20 mg/kg body weight in 0.2 ml of saline. The analysis of propidium iodide stained thymic cell preparations by means of flow cytometry showed that there was a significant increase in the percentage of cells in the S phase (proliferative phase) of the cell cycle of mice injected with colloid (33%) compared with saline injected (15%) and non-injected controls (7%). These findings are the first to suggest that various combinations and concentrations of intraglandular colloid neuropeptides play a role in the immune system and shed light on additional functions of the intermediate lobe.