Early Weanling and Precocious Development of Small Intestine in Rats: Genetic, Dietary or Hormonal Control

Abstract

Summary14); however, its relationship to diet has been explored only to a Small intestinal development was followed in rats from 17 to 28 days of age in order to evaluate the interactions of diets, genetic preprogramming, and hormones in influencing developmental changes. Control pups, weaned naturally at 21-24 days, showed a gradual increase in body weight, intestinal length, and segmental mucosal weight, total DNA, and protein content. In contrast, pups weaned at 17 days showed an immediate increase in intestinal length, decrease in lactase, and precocious increase in sucrase and maltase. The changes in segmental mucosal weight, DNA and protein contents, however, paralleled that of controls. Pups nursed "p to 25 days had a smalle; body weight, shorter intestine, lighter mucosa, and lesser mucosal protein content. They showed no significant delay in the increase in sucrase and maltase together with a persistent higher level of lactase. Enterokinase and leucine aminopeptidase showed little change irrespective of the dietary modifications. Significant increases in segmental mucosal mass, DNA, and protein contents during the studied period were seen in all animals. At 19 days, early weaned pups had serum levels of corticosteroids about 3 times that of control or prolonged nursed pups. The results support the concept of an inherent biologic program as a basic control of intestinal ontogeny whereas dietary changes seem to have a modifying role and act directly, or in concert with, hormonal changes.Neonatal rats have no detectable sucrase, low maltase, and high levels of lactase activities in their small intestines. The activities of sucrase and maltase increase abruptly about the 15th day of age. These two enzymes continue to rise during the third and fourth week with a concomitant decrease in lactase. The third week of life in rats corresponds to the weaning time that is marked by a shift from a fat-rich diet supplied by the mother (4) to a carbohydrate-rich lab-chow diet. The carbohydrate is also changed from an almost exclusive lactose-containing milk to a predominant glucose-polymer-and sucrose-containing chow. A casual relationship exists therefore between dietary changes and the increase in sucrase and maltase with a corresponding decrease in lactase. The possibility of a "dietary influence" of enzymes is further strengthened by the observations that sucrase rises precociously by early feeding of sucrose (15,21). In addition, we have shown (16) that prolonged nursing leads to a slower decline in lactase activity. At 25 days of age, prolonged nursed rats show similar maltase and sucrase activities as control weaned rats. Similar studies by Henning and Guerin (20) also showed no depression in sucrase activities when pups were weaned onto a special diet with lactose as the sole source of carbohydrate. These results are in agreement with those studies using intestinal explants (8,11) or in vitro cultures ( 6 ) and together suggest that the postnatal increase in sucrase and maltase in the rat is preprogrammed. Othe...

Induction of Gastric Ornithine Decarboxylase in Early Weaning Rats

“…Early weaning in rats has been shown to induce precocious expression of sucrase activity, a marker of intestinal differentiation [19, 20]. A study by Lebenthal et al [21]also demonstrated the precocious increases of sucrase activity in suckling rat pups fed with sucrose-containing diet.…”

Postnatal Development of the Exocrine Pancreas in Suckling Goat Kids

“…In rats, corticosteroids are considered as mediators of pancreatic amylase activity development in early weaning (Lee & Lebenthal, 1983b) and in calves the pancreatic activities might be at least partly modulated by gastrin in the first weeks of life (Le Huerou-Luron et al, 1992). When some data are available in this field, they mostly concerned the weaning period (Lee & Lebenthal, 1983a;Henning, 1987).…”

Efeitos tardios do desmame precoce sobre a renovação e diferenciação do epitélio gástrico em ratos.

“…Os mecanismos que coordenam o crescimento e desenvolvimento órgãos podem ser influenciados por fatores genéticos, hormonais e de dietas 121 .…”