Proliferation rate and transit time of mucosal cells in small intestine of the diabetic rat.

Streptozotocin-induced diabetes in the rat alters intestinal function, causes hyperphagia and arrests body growth, but stimulates intestinal growth, particularly in the mucosa. Therefore we measured several indices of epithelial cell proliferation to gain insight on possible factors responsible for the increased mucosal cell mass in the small intestine. We examined epithelial cell proliferation in upper jejunum and terminal ileum of weight-matched control and diabetic rats pair fed or eating ad libitum. Cell proliferation was measured two ways: (1) isolating whole crypts 1 hr after injection of [3H]thymidine ([3H]TdR) and calculating disintegrations per minute per crypt (dpm per crypt), and (2) autoradiography of mucosal sections to obtain labeled cells per crypt, total cells per crypt-villus column, and cell migration rates. Autoradiography showed diabetes: (1) increased cell number of crypt-villus columns and increased labeled cells per crypt section, primarily jejunum, and (2) did not alter cell migration except for an increase in the ileum of diabetics eating ad libitum. Cell proliferation measured as dpm per crypt virtually doubled in diabetics in both segments regarless of dietary regimen. Dpm per crypt is a three-dimensional measurement based on the whole crypt. The increase in cell number and labeled cells per crypt in jejunal sections is also consistent with increased cell division, but shows a much smaller effect. The nature of the histological technique (two-dimensional) limits its usefulness for measuring morphological changes, and this may explain the discrepancy. Hence, the primary effect of diabetes is increased DNA synthesis (dpm per crypt) and this appears to be the main explanation for stimulated mucosal growth.