Effects of guanethidine‐induced sympathectomy on morphology of the pre‐ and postclosure lleum of the neonatal rat

Abstract

The disappearance of the characteristic supranuclear vacuole and extensive apical canalicular system from enterocytes of the ileal villi occurs during the third postnatal week in rats. This phenomenon is associated with loss of permeability of these cells to macromolecules and is therefore termed closure. The present study was designed to analyze the influence of neonatal guanethidine (GTN)-induced sympathectomy on the morphology of the pre- and postclosure ileum of the rat. Light and electron microscopy of control and GTN-sympathectomized rats demonstrated the retention of immature, vacuolated cells on ileal villi as late as 23 days postnatally in GTN-treated rats. Villi from control rats contained only adultlike nonpermeable cells. Electron microscopy further demonstrated no structural differences in the apical canalicular system or storage vacuoles of the delayed cells in GTN rats when compared to the ileal epithelium from preclosure time periods (7 and 15 days) in both GTN-sympathectomized and control rats. Goblet cells were counted on Periodic-Acid-Schiff-stained sections of ileum from 7, 15, and 23-day GTN and control rats. The percentage of goblet cells in the total epithelial cell population of the villus was significantly higher in control versus GTN rats at all time periods. The percentage of goblet cells increased in both groups from day 7 to 15. However, closure in the control group (approximately day 18) was coincident with a steep increase in the percentage of ileal goblet cells which was not evident in the goblet-cell population of the GTN villus. This pattern of change in control versus GTN goblet-cell production was correlated with a similar pattern of variation in the number of crypt cell mitoses between the two groups over the same time period.

Inhibition of azoxymethane‐induced experimental colon carcinogenesis in wistar rats by 6‐hydroxydopamine

“…N E released by the action of the sympathetic nervous system appears to stimulate crypt-cell proliferation in both the small and the large intestine (Tutton and Helme, 1974;Tutton and Barkla, 1977). Neonatal sympathectomy inhibits ileal epithelial-cell proliferation (Klein and McKenzie, 1980), reduces the amplitude of the mitotic circadian rhythm (Klcin, 1981), and retards the morphologic characteristics of ileal closure (McKenzie and Klein, 1982). In the present work, we found that prolonged administration of 6-OHDA resulted in a significant decrease in the labelling index of colon epithelial cells.…”

Effect of Sympathectomy on Ontogeny of Small Intestinal Disaccharidases in the Rat

“…In sympathectomized rats this clo sure phenomenon is delayed. Closure is also usually associated with a dramatic increase in the number of goblet cells, which was not evident in the sympathectomized animals (5).…”

“…Several studies have documented the effect of guanethidine-induced sympathectomy on intestinal epithelial cell proliferation and morphology in the neonatal rat. Sympathectomy inhibits neonatal ileal cell proliferation and delays the dramatic increase in crypt cell mitotic and labeling indices normally seen at 18 days of age (3)(4)(5). Immature vacuolated cells, permeable to macromolecules, normally disappear from ileal villi by 23 days of age .…”

“…Mo st of the se factor s ha ve been e xt en sivel y stud ied , but th e role of the sy mpathe tic s ystem in the regulation of postnatal intestinal de velopment ha s only recently been addre ssed. Neonatal sympathectom y inhibits ileal e pithe lia l cell prol iferat ion (3), reduces th e amplitud e of mitotic circadi an rhythm (4) , and retards the morphologic ch aracterist ics of ileal closure (5).…”

The Role of Cell Renewal in the Ontogeny of the Intestine. II. Regulation of Cell Proliferation in Adult, Fetal, and Neonatal Intestine

“…The delay in acceleration of mitosis also retards morphological characteristics of closure (197). Immature.…”