Polyploidy and nuclear phenotypes in salivary glands of the rat

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Abstract
This work describes polyploidy characteristics and nuclear phenotypes with advancing age in salivary glands of the rat. Feulgen‐stained nuclei from squashed salivary gland fragments and nuclei isolated from homogenized salivary glands were analyzed with automatic scanning cytophotometry using Zeiss equipment and a Microdata computer. Polyploidy was demonstrated even in the submaxillary glands of young animals which exhibited 2C and 4C Feulgen‐DNA classes. Glands from 1.5 year‐old rats displayed diploid, tetraploid, and octaploid nuclei. Parotid glands from young animals exhibited Feulgen‐DNA values pertaining to 2C, 4C, and 8C classes, whereas those from aged animals exhibited values pertaining to these classes and to the 16C one. The polyploid nuclei of both glands showed mean absorbances higher than those of diploid nuclei, which is assumed to be due to an increase in the chromatin packing state accompanied by redistribution of the heterochromatin areas. Feulgen‐DNA values ‐nuclear surface and average absorption ratio‐ surface covered by condensed chromatin correlations support these assumptions.