A morphometric study of seasonal influences on the daily cycle of rat submandibular glands

RESUMO

The submandibular glands of rats raised at room temperature show daily and seasonal variations. To quantify these variations, the submandivular glands of male Wistar rats were collected at 4h intervals over a 24h period in the summer and winter and processed for histological analysis. Gland weight decreased 37 per cent (P<0.01) in the winter and 13 per cent in the summer. The volume of the acinar compartment decreased 73 per cent (P<0.01) between midnight and 4 a.m. in the winter and 38 per cent (P<0.01) between 8 p.m. and midnight in the summer. In contrast, the volume of the stroma increased about 164 per cent (P<0.01) between midnight and 4 a.m. in the winter and by 10 per cent (P<0.01) between 8 p.m. and midnight in the summer. the volume of the duct system generally remained constant, although in the winter the convoluted granular tubules diminished 44 per cent (P<0.01) between midnight and 4 a.m. Although the volume of the intercalated ducts remained constant over 24h in both seasons, there was a 49 per cent decrease in winter compared to summer (P<0.01). These results indicate that the large changes in gland weight were caused mainly by variation in the volume of the acini, convoluted granular bubules ans stroma. The morphological variations were much more pronounced in winter than in summer and this affected the daily saliva production.