Balance of amino acids in the pregnant human uterus at term

Neutral and Cationic Amino Acids in Striated Rectus Muscle Are Generally in Excess of Those in Smooth Uterine Muscle of Term Pregnant Women

“…This suggests little net utilization of amino acids during late gestation by uterine tissues and placenta [16]. This is again concordant with our findings in a previous study on arteriovenous differences, showing little or no net uptake of amino acids in term pregnant uterus [11],…”

“…Although insulin has been shown to augment protein synthesis in vitro [26][27][28], a similar anabolic effect in vivo has been difficult to establish [20][21][22][23]. Hence, although insulin decreases protein break down, it does not increase steady state net amino acid uptake from the plasma pool [29] which may tally with our previous findings [11]. The neutral amino acids gly cine, alanine, and threonine and the dccarboxylated ami no acid glutamine showed the greatest negative arteriove nous differences [11] which corresponds to our present findings of low concentrations in the uterine muscle as compared with the rectus muscle.…”

“…This was of considerable interest in the light of our previous findings that the arteriovenous dif ferences of amino acids at term are generally negative, i.e., there is a release of amino acids in most cases at term [11], Rapid changes in the distribution pattern may theoreti cally only reflect alterations in the intracellular pool of free amino acids [12], However, in a more prolonged per spective, a net balance of amino acids will provide predic tive information regarding net protein balance. Hence, a prolonged negative balance of amino acids will corre spond to a negative protein balance, since a continuous efflux from an organ will influence the free intracellular amino acid pool to such an extent that it must soon Mean value, range, and standard error of the mean (SEM) are given.…”

Human Uterine Myocytes Retain Their Energy Charge with No Gross Alterations in Morphology for at Least 8 Days when Cultured under Anaerobic Conditions

“…The same pattern was discerned regarding the low myometrial glycogen content in comparison with the rectus-striated muscle in term pregnant women [4]. Substrate uptake studies disclosed that the human uterine smooth muscle at term rather released than accumulated amino acids, free fatty acids and glycerol [5,6], while glucose, which occurs in much higher concentrations in Olovsson/Nordling/Ulmsten/Lindblom/ Waldenström/Ronquist myometrium than in striated muscle [4], seemed to be the principal and sole energy substrate [6]. The coefficient of extraction of glucose was 7.3% across the uterus as measured by glucose uterine arteriovenous difference [6].…”

Low Myometrial Glycogen Content Compared with Rectus Muscle in Term Pregnant Women before Labor

“…Furthermore, prolonged tonic contractions in human uterine muscle strips were associated with only small changes in the adenylates indicating near equilibrium conditions between ATP breakdown and ATP resynthesis [5]. Substrate uptake studies revealed that the human uterine muscle at term rather released than accumulated amino acids, free fatty acids, and glycerol [6,7], and glucose seemed to be the principle and sole energy substrate [7]. Therefore, the glycogen store would be another conceivable energy substitute for the pregnant myometrium.…”