Effect of intrauterine growth retardation on the activities of fetal intestinal enzymes in rats.

The activities of maltase, lactase, alkaline phosphatase and enterokinase were followed in the small intestine of rats during prenatal development. These enzymes were detectable only after the 17th day of gestation. Furthermore, each enzyme exhibited a different pattern of prenatal presence. Maltase activity appeared first (day 18), followed by lactase and alkaline phosphatase (day 19) and then enterokinase (day 20). Except for enterokinase, all of the enzymes attained a level of activity close to the newborn levels at the final day of gestation. Induced intrauterine growth retardation during the 3rd trimester led to a decrease in intestinal weight proportional to the reduction of body weight. These decrease in size of the small intestine was caused by a reduction in cell number rather than cell size. Induced intrauterine growth retardation also resulted in a selective reduction in the specific activities of lactase and alkaline phosphatase, but not of enterokinase and maltase. These results suggest that reduction in maternofetal blood flow in the 3rd trimester of gestation will cause a selective decrease in some brush border enzymes (lactase and alkaline phosphatase) but does not effect others (maltase and enterokinase).

The effect of reduced maternofetal blood flow on the development of fetal pancreatic acinar cells and enzymes.

It has been noted that from days 18 to 22 (birth) during the second intrauterine period of morphogenesis of the rat pancreas the accumulation of enzymes increases dramatically. We studied the effect of altered maternofetal blood flow on the development of the rat pancreas during the critical second period. Our studies indicate that during pancreatic cytodifferentiation, reduction in maternofetal blood flow not only reduces the weight of the pancreas (68% of control) and diminishes the total activities of enzymes but that the changes in specific activities of the enzymes do not appear to be coordinate. The specific activities of amylase decreased to 59,000 units from the control value of 103,000 units (P less than 0.01) and lipase decreased to 4000 units from a control value of 7350 units (P less than 0.001). In contrast, the specific activities of trypsin (ogen), chymotrypsin (ogen) and (pro)-carboxypeptidase A and B are not changed. These results suggest that reduction in maternofetal blood flow caused a selective decrease of fetal rat amylase and lipase during the third trimester of gestation.