Regional differences in the distribution of dividing cells in hamster cheek pouch epithelium

Examination of vinblastine-arrested metaphase figures in sections from the medial wall of 15 hamster cheek pouches showed that: (1) the distribution of dividing cells was non-random and (2) mitotic activity declined in an anteroposterior direction. Although there was some variation between different pouches these features were statistically significant (P less than 0.05) in individual pouches from half the animals and highly significant (P less than 0.005) when the data from all pouches were pooled. The average sample size required to determine a mitotic index representative of the whole length of the pouch was equivalent to approximately 32 mm of surface length of epithelium or 4562 basal cells. This estimate exceeds the sample size generally examined and it is suggested that inadequate sampling could account for some of the inconsistencies in the literature on hamster cheek pouch cell kinetic data.