Syntheses of guanidinoacetate and creatine in maternal tissues and placentae of gestating gilts fed diets with or without supplemental creatine.

This study determined the effects of dietary supplementation with creatine to gestating gilts (n = 6) on their ability to form guanidinoacetate (GA) and creatine in placentae and maternal tissues. Gilts were assigned randomly to one of two dietary groups: control and creatine supplementation (Cr; n = 12 gilts/ diet). Once estrus was detected (d 0), gilts were artificially inseminated 12 h and 24 h later. All gilts were individually housed and fed 0.9 kg of a corn- and soybean-based diet containing 14% crude protein (but no creatine or GA) twice daily. Gilts in the control and Cr groups received daily top dressing of 0 or 2 × 15 g Cr either between d 10 and 60 or between d 10 and 90 of gestation. There were 6 gilts per dietary treatment per gestational stage. On either d 60 or 90 of gestation, gilts were euthanized to collect maternal tissues and placentae. Each tissue (~150 mg) was incubated at 37 ℃ for 2 h in 2 mL of oxygenated (95% O₂ /5% CO₂ ) Krebs bicarbonate buffer with or without a) 2 mM glycine plus 2 mM L-arginine or b) 0.2 mM GA plus 0.5 mM L-methionine (the source of S-adenosylmethionine). After the 2-h period of incubation, 0.2 mL of 1.5 M HClO₄ was added to the medium. The acidified medium plus tissue was homogenized and the homogenizer rinsed with 1 mL water, followed by the addition of 0.1 mLl of 2 M K₂CO₃. The extract was analyzed for GA, creatine, and amino acids using HPLC. Results indicated that on both d 60 and 90 of gestation, a) GA was formed from glycine plus L-arginine by maternal kidneys and pancreas of all gilts, but not maternal liver, placentae, or endometria; b) GA was converted into Cr by both maternal liver and pancreas, but not maternal kidneys, endometria, or placentae; c) dietary supplementation with Cr did not affect (P > 0.05) either the formation of GA from glycine plus L-arginine in maternal kidneys and pancreas or the conversion of GA into creatine in maternal liver and pancreas (Tables 1 and 2). Collectively, these results indicate interorgan cooperation to form creatine in pregnant gilts to support fetal growth and development, as well as the lack of inhibition of this metabolic pathway by dietary supplementation with creatine. [ABSTRACT FROM AUTHOR]