Pattern of crypt cell proliferation in the pre- and post-closure ileum of the neonatal rat: effects of sympathectomy.

The present experiments were designed to investigate ileal crypt cell division before and after neonatal closure to macromolecular absorption by measurements of mitotic index, labelling index, colchicine-induced estimation of mitotic rate (mitoses/cell/hour) and crypt depth and villus height on postnatal days 15--23. In addition, the effects of the sympathetic nervous system on crypt cell proliferation were analyzed by guanethidine-induced sympathectomy. Guanethidine treatment resulted in at least a 70% reduction in superior cervical and coeliac perikarya at 15 days after birth. All cell proliferative indices demonstrated a rather constant rate of cell division in the ileal epithelium between 15 and 17 days after birth with a sudden burst of mitotic activity on day 18. The mitotic rate of control rats increased from day 18 to 23 with 3-week-old rat demonstrating a faster rate of ileal crypt cell proliferation than adult rats. The ileal crypt depth more than doubled between 15 and 23 days while the height of the villus column increased slowly but steadily (36%) during the period of this study. Cell division is inhibited by guanethidine-induced sympathectomy although there is still an acceleration of mitosis in the post-closure period. The relationship of sympathectomy and ileal crypt cell proliferation is discussed and compared to hormonal effects on closure and related developmental events.