The effects of pregnancy and lactation on the activities of trypsin and α-chymotrypsin in the rat pancreas

Abstract

I . The food intake, pancreas weight and trypsin (EC 3 . 4 . 2 1 . 4 ) and a-chymotrypsin (EC 3 . 4 . 2 1 . I ) activities in the pancreas were measured in rats during pregnancy and lactation and after the young were weaned.2. All the quantities measured increased significantly during lactation and had returned to their original values by 4 weeks after weaning. Food intake and pancreas weight were highest after the second week of lactation. Total trypsin and a-chymotrypsin activity, and the activity per g tissue, fell during pregnancy and rose during lactation, reaching a maximum I week after weaning. 3.From these and other results it is suggested that the hypertrophy and hypersecretion of pregnancy and lactation are initiated by changes in insulin secretion and mediated by the trophic effects of gut hormones, and that differences in the nature and timing of the response may be controlled by nutrient availability.

Activities of some metabolic enzymes in the small intestinal mucosa during pregnancy and lactation in the rat

“…These experiments show that some metabolic enzymes, like the digestive enzymes investigated in previous work (Rolls, 1975;Rolls et al, 1979), increase during pregnancy and lactation in the rat and that, at least in some instances, these increases are in excess of those expected simply from enlargement of the gut. These changes in total activity can be contrasted with the findings of Burdett, Green & Reek (1978) who studied a range of metabolic enzymes in different regions of the gut histochemically and reported some increases in activity during pregnancy but, in general, no further increases in lactation.…”

“…Some of the changes produced by pregnancy and lactation in various extra-reproductive organs have been reviewed by Fell (1977) and Rolls, Henschel & Palmer (1979). In particular, we have shown that the activities of some enzymes responsible for protein digestion are increased in the small intestine (Rolls, 1975) and in the pancreas (Rolls et al, 1979), slightly in pregnancy and markedly during lactation.…”

“…In particular, we have shown that the activities of some enzymes responsible for protein digestion are increased in the small intestine (Rolls, 1975) and in the pancreas (Rolls et al, 1979), slightly in pregnancy and markedly during lactation. In the present experiments, 4 metabolic enzymes were studied to investigate whether their activities alter during the reproductive cycle and whether any changes can be related to the general gastrointestinal enlargement or to the variations in digestive capacity.…”

“…It is tempting to envisage a connection between this and the fall in pancreas weight and proteolytic enzyme activity (Rolls et al, 1979), but if the pancreatic effect is the result of restricted nutrient availability it would seem improbable that such an explanation could apply to an intestinal enzyme activity, particularly as no other intestinal function investigated was altered.…”

Decrease in amylase (EC3.4.21.4) synthesis in lactating rats

“…In the late stage of pregnancy and during the lactation period, hypertrophy and hyperplasia of the gastrointestinal organs occur, such as an increase in the weight of the stomach, increase in the intestinal mucosal surface area, hyperplasia of the small intestinal epithelium and increase in crypt length and villus height (Crean & Rumsey, 1971 ;Cripps & Williams, 1975;Rolls, 1975;Jolicoeur et al 1980;Remesar et al 1981). These changes are induced by increases in the plasma level of gastrointestinal hormones such as gastrin, secretin and cholecystokinin (CCK), which have been shown to have significant trophic effects on the gastrointestinal organs (Rolls et al 1979). Gastrin and CCK stimulate not only the secretion of exocrine pancreatic enzymes but also their synthesis in the acinar cells (Mainz et al 1973;Barrowman & Mayston, 1974).…”