Free Amino Acids in Plasma and Tissue of Rats Born to Underfed Dams

Abstract

The importance of prenatal and postnatal nutrition on the development of the progeny has been well documented. Severe food restriction results in infertility in women (1). Maternal malnutrition in rats retards DNA replication and the synthesis of RNA and protein (2-4). Results from our laboratory have shown that underfeeding of the dams during gestation and lactation had an adverse effect on the growth rate of the offspring (5). These stunted animals required more feed for growth and excreted more urinary nitrogen, urea, total amino acid ( 6 ) , and hydroxyproline (7) than the controls. These changes suggest that the growth stunting may be related to some aspects in protein metabolism. The present experiment was undertaken to determine the effect of maternal dietary restriction on free amino acids in plasma, liver, and muscle of the progeny .Materials and Methods. Animal and diet. Male rats of the McCollum strain were used. They were housed individually in stainless steel cages at room temperatures of 25-28" during the whole experiment. The method of maternal dietary restriction has been described in detail elsewhere (7). The following comparisons reported are between groups of male rats born of mothers on ad libitum feeding of Purina Chow and groups born of the mothers restricted during gestation and lactation to approximately 0.5 the amount of feed consumed by the control group. After 28 days of age, all progeny were housed individually and received Purina rat chow. Fresh water and food were freely available.The weights of rats, as well as their food intake, were recorded weekly. At the end of 9 mo, the animals were fasted for 18 hr and then killed by decapitation. The fasting blood was collected in a heparinized tube, and the plasma was separated and stored in a freezer at -25". The liver and a portion of gastrocnemius muscle were removed quickly and frozen in -80" until analyzed.Amino acid analysis. An aliquot of each tissue was homogenized in distilled water to yield a 5% homogenate. This was followed by centrifugation after which the tissue supernatants and the plasma were deproteinized with equal volumes of 9% sulfosalicylic acid. Amino acids were analyzed by ion-exchange chromatography on 140 X 0.62 cm single column with a Technicon amino acid analyzer. Gradient elution was carried out with sodium citrate buffers (a) pH 2.88 (0.2 N for Na+) and (b) pH 4.74 (0.8 N for Na+), prepared as described in Technicon Monograph No. 1, 1966. Norleucine (0.125 p M ) was always included as an internal standard and a commercially prepared amino acid standard was analyzed periodically. The data were analyzed statistically by means of Student's t test.Results. During the 9-mo experimental period the food intake, calculated as gram per unit body weight, was consistently about 20% higher among the offspring of underfed mothers than ad libitum-fed mothers. The mean body weight for the restricted progeny was 285 & 31 g which is about 75% of normal value. This difference is statistically significant.The concentrations of plasm...

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