摘要：

A comparison has been made in vivo between L(+)-3-hydroxy[3-14C-]butyrate, P(-)-3-hydroxy[3-14C]butyrate, [3-14C]acetoacetate, and P-[2-14C]glucose for sterol and fatty acid synthesis and respiration in the 18-day-old suckling rat. Sterols and fatty acids in spinal cord, brain, and skin were preferentially labeled by these metabolites over sterols and fatty acids in the liver and kidneys. More label was incorporated into sterols and fatty acids in spinal cord, brain, and kidneys from L(+)-3-hydroxy[3-14C-]butyrate than from P(-)-3-hydroxy[3-14C]butyrate. More label was incorporated into sterols and fatty acids in spinal cord, brain and skin from D(-)-3-hydroxy[3-14C]butyrate than from [3-14C]aceroacetate. In all organs less label was incorporated into sterols and fatty acids from D-[2-14C]glucose than from the other metabolites; unexpectedly poor were the liver and kidneys which contained substantially less label. The retention of label from D(-)-3-hydroxy[3-14C]butyrate in the sterols and fatty acids from spinal cord and brain was investigated. The time course of evolution of 14CO2 over 2 1/2 hr from each of these metabolites revealed a more rapid utilization of [3-14C]acetoacetate maximum at 10 min than P(-)-3-hydroxy[3-14C]butyrate maximum at 30 min; by contrast, label from D-[2-14C]glucose and L(+)-3-hydroxy[-14C]butyrate was retained maximally in metabolic pools over a 2 hr period, indicating a much slower utilization. The evidence that the L(+)-3-hydroxy[3-14C]butyrate is a favored substrate for the synthesis of sterols and fatty acids but less favored for oxidation, while D(-)-3-hydroxy[3-14C]butyrate is a favored substrate for oxidation but less favored for the synthesis of sterols and fatty acids, suggests that these isomers are preferentially metabolized in different compartments.

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