On the basis of the circadian oscillations of the rat's exocrine pancreatic function and previous reports on concomitant ultrastructural changes in thc pancreatic tissue, we analysed stereologically the circadian rhythmicity in the structure of this organ. Twenty-four male Wistar rats, four and a half months old, were singly housed two months before the experiment in a lighting regimen LD = 12:12, constant environmental temperature and relative humidity, with food and water ad libitum. The experiment was performed in winter. The rats were randomly divided into 6 balanced groups and killed under ether anesthesia at 6 equidistant time points in 24 hours. The pancreatic tissue was fixed in glutaraldehyde and osmium and embedded in Epon. 1 μm thick sections were examined by light microscopy for the evaluation by stereological methods of: a) volume fractions of the different parenchymal components of the exocrine pancreas; b) surface fractions of acinar cell faces; c) size distribution of acinar cell nuclei, their number per unit tissue volume and their mean diameter. Single cosinor method analysis of the data demonstrated statistically significant circadian rhythms for the volume fraction of the cytoplasm of acinar cells and the volume fractions of pancreatic acini and acinar cells. The volume fraction of the cytoplasm of the rat pancreatic acinar cells undergoes circadian oscillations with the highest values at the end of the light span; this rise precedes the well-known physiological nocturnal surge of pancreatic digestive enzymes. Our findings further support the hypothesis of a close relationship between pancreatic cell structure and its function.
|Titolo:||Circadian rhythm of rat pancreatic acinar cells|
MONTARULI, ANGELA (Primo)
DOLCI, CLAUDIA (Secondo)
CARANDENTE, FRANCA (Ultimo)
|Data di pubblicazione:||1997|
|Appare nelle tipologie:||01 - Articolo su periodico|