Modifications of Brush Border Enzyme Activities during Starvation in the Jejunum and Ileum of Adult Rats

Abstract

Aminopeptidase, lactase and sucrase activities have been followed during 5 days in the jejunum and in the ileum of starved adult rats. Enzyme activities have been determined in the mucosal homogenates as well as in the purified brush border membranes and expressed as activities per intestinal length (segmental activities) or as activities per milligram of protein (specific activities). The segmental and specific activity of aminopeptidase was increased in the ileum during the first 2 days of starvation, suggesting that aminopeptidase may have during the first days of starvation a conservative role by preventing an important loss of tissue protein. In all conditions, lactase activity was strikingly enhanced by starvation whereas sucrase activity showed no changes or decreased activity. Lactase stimulation was initiated during the first 24 h of starvation reaching its maximum after 2 days. The various experimental conditions leading to a specific or to a nonspecific stimulation of intestinal lactase activity have been discussed.

Intestinal disaccharidase and dipeptidase activities in growing rats fed on a raw field bean diet

“…The dependence of enzymic activities upon the level and nutritive value of protein has been repeatedly reported. [15][16][17][18][19] In that context, the growth depression caused by raw legume seeds, in the diets of experimental animals-which has been attributed to the occurrence of some anti-nutritive factors5 or to a low suphur amino acidic content6-is accompanied by changes in the activity of enzymes involved in different metabolic pathways: cathepsins,zo guanidinoacetate methy1transferasez1 and other^.^^,^^ Furthermore, it has been reported that activities of both trypsin and cr-amylase were significantly reduced in rats consuming diets from a coloured variety of Vicia fubu (rich in tannins), whilst those receiving diets from a tannin-free variety had comparable values to those fed a control diet. In contrast, lipase activity was increased.…”

The effects of hibernation on the myenteric plexus of the golden hamster small and large intestine

“…During the torpid phase of hibernation the gut is subjected to periods during which there is no food intake. The absence of luminal contents (Raul et al 1982) and the process of hibernation itself (Carey 1990) are reported to cause changes in intestinal structure and function. A lack of luminal contents is known to cause atrophy of the intestinal mucosa and smooth muscle and can lead to alterations in gut function (Raul et al 1982;Karasov and Diamond 1983) in species which do not hibernate.…”

“…The absence of luminal contents (Raul et al 1982) and the process of hibernation itself (Carey 1990) are reported to cause changes in intestinal structure and function. A lack of luminal contents is known to cause atrophy of the intestinal mucosa and smooth muscle and can lead to alterations in gut function (Raul et al 1982;Karasov and Diamond 1983) in species which do not hibernate. Carey (1990) has reported changes in mucosal structure and transport function in hibernating ground squirrel intestine.…”

Modulation by Thyroxine of the Amount of Lactase Protein in the Jejunum of Adult Rats

“…The starvation-induced stimulation of lactase reaches a plateau after 48 h [7] and is restricted to the mature enterocytes [9]. Lac tase is the only disaccharidase to be stimu lated by starvation in the jejunum of adjult rats and, as shown previously, the stimula tion process involves hormonal effect: thy roid hormones are acting normally as a neg ative effector for lactase activity [9-11] and starvation by lowering the level of circulat ing thyroid hormones provokes a stimula tion of intestinal lactase [9],…”

“…The molecular mechanism acting in the developmental de cline of intestinal lactase activity remains to be elucidated. However, in adult rats, stimu lation of lactase activity has been reported either following carbohydrate ingestion [2][3][4][5] or during starvation [6,7],…”