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...

L-Carnitine enhanced glycerol release from new born subcutaneous adipose tissue fragments with or without simultaneous stimulation with isoproterenol (10^––5 M) or theophylline (10^––3 M) (p ≤ 0.05). Deoxycarnitine (2.5 mM) decreased lipolysis under similar conditions (p ≤ 0.05). The optimal concentration of L-carnitine (10^––3 M) was determined by a dose response curve in isolated neonatal adipocytes. In adult subcutaneous adipose tissue fragments, L-carnitine increased lipolysis only in the presence of the β-stimulator isoproterenol (10^––5 M) (p ≤ 0.05), while deoxycarnitine had no effect.