Inositol Phosphatase in Developing Rat Duodenum, Jejunum and Ileum

Abstract

Inositol phosphatase and phytase activities in different segments of the rat small intestine were measured during postnatal development. In the duodenum and jejunum, inositol phosphatase activity (units/g tissue) was low during the suckling period and increased at weaning, reaching a peak of activity at 4 weeks of age. In the ileum, peak activity was observed during the suckling period with a sharp decline at weaning. Phytase activity was very low during the suckling period in all segments, and increased to exhibit a peak at 4 weeks of age in the duodenum, and to a lesser extent in the jejunum (low activity was maintained in the ileum). The content of inositol phosphatase activity in the duodenum increased rapidly during the suckling period to reach its maximum at 4 weeks of age. This suggests a relationship to cell proliferation rate in the small intestinal mucosa.

Effects of Postweaning Protein Malnutrition on Intestinal Inositol Phosphatase Activities in Normally Weaned and Neonatally Undernourished Rats

“…In our present studies, intestinal phytase activity was also altered by protein malnutrition. The effects were parallel to the effects on inositol triphosphatase activity, except that , in contrast to inositol triphosphatase, phytase activity per milligram of DNA in duodenum and jejunum was significantly elevated by postweaning protein malnutrition in normally weaned rats, supporting our previous observations (18,19) that inositol triphosphatase and phytase are two distinct enzymes.…”

“…The body weights of surviving rats were 81% lower than those of control Imposition of postweaning protein malnutrition on normally weaned rats resulted in a retardation of body and intestinal growth. Body and intestinal weight of these protein deficient rats is comparable with that of 3-4-week-old normally nourished rats of the same colony (18). Effects of post weaning protein malnutrition were more severe in the neonatally undernourished rats (L -P-) than in normally weaned rats (L +P-).…”

“…Duodenum, jejunum, and ileum of small intestine possess distinct morphological, functional , and developmental differences. Our previous studies have demonstrated regional differences in the maturation of inositol triphosphatase and phytase activities in developing rats (18). Therefore, variations of the findings with gut location may suggest an independent regulation of PPI metabolism in the different regions of small intestine, possibly involving different functions .…”

“…The polyphosphoinositide (PPI) signal transduction system is known to regulate a number of cellular processes such as metabolism, secretion, contraction, neural activity, and cell proliferation (15). A rapid increase of lipid-bound inositol concentration (16), triphosphoinositide (TPI)-specific phospholipase C activity (17), and inositol triphosphatase activity (18) in small intestine during neonatal period indicates a possible role of PPI in the maturation of the small intestine. A marked decline in TPI-specific phospholipase C activitiy, with a slightly lower TPI concentration (17) and an elevated ileal inositol triphosphatase activity (19), suggest an altered PPI metabolism in the small intestine during neonatal undernutrition.…”