STEREOLOGICAL STUDY OF ACINAR GROWTH IN THE RAT PAROTID-GLAND INDUCEDBY ISOPROTERENOL

The growth of the rat parotid gland induced by daily treatment with is oproterenol (IPR) for 2 weeks was investigated by stereological method s applied to light microscopy. After 7 days of treatment, the glandula r mass presented a 286% growth, with the first 3 days being the period of greatest growth. Total acinar volume exhibited a 363% increase dur ing the period from 0 to 7 days, while acinar-cell volume presented a 468% growth from 0 to 5 days of treatment. On the other hand, total ac inar-cell number did not increase during the study period. Thus, under the conditions used, IPR-stimulated gland growth wits essentially hyp ertrophic. However, a significant increase in the number of bipolar an d multipolar mitoses was also observed, especially on the third and fi fth days of treatment. As no increase in acinar-cell number occurred d uring growth, the presence of these mitoses suggests that cell death o ccurred during gland growth. On this basis, bipolar mitoses may occur to replace cells that probably degenerated during treatment, whereas m ultipolar mitoses may lead to the occurrence of polyploidy. (C) 1997 E lsevier Science Ltd.