Carnitine Content of Blood and Amniotic Fluid

Abstract

Free carnitine levels \rere determined i n amniotic fluids bettfeen the 10th ancl 40th \reek of gestation. 'l'liey were founcl to tlecrease significantly \\ith gestational age. illood levels of carnitine were lower i n pregnant than in nonpregnant \vonien. Levels were found to be higher in cord I~l o o d thari i n niaterrial hlood and usually were higher in the uriibilical artery than vein. Intraarterial injection o f L-carnitine into a pregnant ewe (lid not cause a rise in the fetal hlood level o f carnitine, trhich, i n contrast to hunian fetal blood, contained less thari half the level of c:~rnitine i n niaternal blood. Speculation I t is suggested that the placenta niay play a role i n carnitirie transport fro111 niother to fetus ant1 that fetal blood and ariiriiotic fluid levels riiay reflect retention o f carriitirie by fetal tissues.L-carnitinc (trimetliyl:rminoliyc1rosyl~utyric acid) is necessary for optimal transfer of ;~cyl groups across mitocliondrial m e nhrancs and thus for niitochondrial fatty acid osidirtion (5). Several enzymes. collectively calleel carnitine acyltransfcrases, arc responsible for the reaction Acyl-CoA + c;~rriililic = ~tcylc~trnltinc + CoA Since in most n~ammals, including man, the rate of fatty acid osid;rtion is l o~v in fetuses and increases rapiclly after birth. as evidenced, for csample, by the lo\v rate of ketone production hy fetal rat liver in comparison to liver from ne\vbor~i animals (4. 10). it ~o u l d appear that the need for carnitinc ancl the tramfcrases should be higher post-than prenatally. This has hccn s h o~' 1 1 to be the C;ISC i l l the rat where carnitine content and carnitine acyltransfcrase activities increase soon after birth in liver ( I ) , heart, hro\vn fat, and even hrain (7). In fact. i t has heen suggested that the tissue \vliicli utilizes tlie I:~rgcst amounts of FA also contains the 1;rrgcst amount of carnitinc and tlic highest transfer;~sc activity (G). We have shoivn th;~t. in contrast to the rat, human (6) :rnd monkey (9) fetal tissues shoiv relatively high transferasc activities. In :rdclition. injection of [l'C]carnitinc into pregnant rats results in the appearance of the lahcl in ;rmniotic fluid (1 1).In vie\\. of tlic above. \vc consiclerccl it of intercht to examine the carnitine content of human irmniotic fluicl and umbilical and maternal hlood.Amniotic fluid ( A F ) was obtainecl from fetuses aged 9-40 \vecks. either during dclivcry or by iumnioccntc~i~ or during legal abortions. Umbilical blood and m:rternal vcnous blood were collected at the timc of delivery.Carnitine in i\F \vas usu;illy determineel \\.ithout prior dcproteinization. 13loorl seruln \\.:IS clcproteinizcd \\.it11 either pcr-X chloric acid o r barium hyclroside and zinc su1f;rte. After neutralization and centrifugation, tlic supernatant \vas assayed for carnitinc.Carnitine \\as clctcrmined by an automated mcthocl clevelopcd by us (12). Somctinics the r:~tlionctivc method of Ccderhlad anel Lindstcdt (2) was used. particularly for A F , \vlierc Ic\,cls \\.ere l o~v .No att...

Fatty acid oxidation and ketogenesis during development

“…Since the fetus has a very limited ability to synthesize carnitine (Hahn, 1981), it is entirely dependent upon the placental transfer of maternally-derived carnitine. In rats and sheep the placental transfer of carnitine is poor (Hahn and Skala, 1975 ;Hahn et al, 1977), as is the transport of NEFA, and it is not surprising that fatty acids do not contribute significantly to fetal oxidative metabolism (Battaglia and Meschia, 1978 ;Girard, Pintado and Ferré, 1979 ;Girard and Ferré, 1982). In rabbits and guinea-pigs the placental transfer of both carnitine (Hahn, Seccombe and Towell, 1981) and NEFA is rapid but, despite an adequate supply of these, the fetal tissues do not oxidize fatty acids.…”

Carnitine Status at Birth of Newborn Infants of Varying Gestation

“…Ketones constitute a significant source of metabolic fuel, particularly for utilization by brain in the perinatal period (18). These various studies seem to indicate that carnitine is one of the essential nutrients in the diet of newborn infants (3).EStudies in various animal species have demonstrated a transfer of carnitine from the mother to the fetus during pregnancy and via milk during the postnatal period (10,11,20). The amount of carnitine transferred across the placenta varies with different species.…”

Comparison of the Effects of Betamethasone and L-Carnitine on Dipalmitoylphosphatidylcholine Content and Phosphatidylcholine Species Composition in Fetal Rat Lungs

“…guinea pigs (17), there is a demonstrable increase of both free L-carnitine and L-acetylcarnitine levels in fetal rat lungs following the maternal administration of relatively small amounts of carnitine. Hahn et al (16) were able to show that injection of [I4C]carnitine into pregnant rats resulted in the appearance of the label in amniotic fluid. It is of interest to note in this context that in man levels of both free and acetylcarnitine have been found to be higher in cord blood than in maternal blood, suggesting placental transfer to be adequate (16,19).…”

“…Hahn et al (16) were able to show that injection of [I4C]carnitine into pregnant rats resulted in the appearance of the label in amniotic fluid. It is of interest to note in this context that in man levels of both free and acetylcarnitine have been found to be higher in cord blood than in maternal blood, suggesting placental transfer to be adequate (16,19). As in rabbits and guinea pigs, there is a high carnitine tissue level even before birth (1 8); these species are unsuitable as experimental models for studying carnitine metabolism in fetal lungs, since such findings cannot be extended to human fetal lungs.…”

“…The PC-32 monoenic species can be characterized as 16 3.3%) groups. These differences in PC species composition are also manifested in quantitative terms (Fig.…”