[Cytologic mechanisms of postnatal growth of adrenal chromaffin tissue].

We have studied the contribution of proliferation and hypertrophy of glandular cells to the ontogenetic growth of adrenal chromaffin tissue using several methods (organometry, cytometry, cytophotometric quantitation of DNA in the nuclei, radioautographic analysis of 3H-thymidine incorporation, calculation of the mitotic index and proportion of binuclear cells, as well as stereological analysis). Mitotic division of diploid glandular cells is the main cellular mechanism of postnatal growth of chromaffinocytes. It is most prominent during the first 2 weeks of life and is maintained at a rather high level throughout the life of animals (the daily proliferative pool in 6-month-old and 30-month-old rats equals 0.3%). Development of cellular hypertrophy has been noted during the first 6 months after birth. The population of chromaffinocytes throughout life is practically diploid; the proportion of tetraploid (binuclear) cells does not exceed 1-1.5%. The growth of adrenal chromaffin tissue during the first month of life is generally supported by hyperplasia and hypertrophy of norepinephrocytes and later of epinephrocytes. The contribution of cell proliferation and hypertrophy to postnatal growth of each subpopulation appears to be equal.