Freetly H C, Ferrell C L
USDA, ARS, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, NE 68933, USA.
J Anim Sci. 2000 May;78(5):1380-8. doi: 10.2527/2000.7851380x.
The objective of this study was to determine the pattern of nutrient flux across portal-drained viscera (PDV) and liver in ewes with varying numbers of fetuses. Catheters were placed in the hepatic portal vein, a branch of the hepatic vein, a mesenteric vein, and the abdominal aorta of each ewe. Plasma flow and net cholesterol, nonesterified fatty acids (NEFA), and glycerol release across the PDV and liver were determined prior to exposure to rams. Ewes were subsequently mated. Two ewes were not pregnant, six ewes gave birth to singles, and 11 ewes gave birth to twins. Additional measurements were taken 103, 82, 61, 39, 19, and 6 d before parturition. There was a net PDV uptake of nonesterified cholesterol in the nonpregnant ewes and a net release in the ewes with singles and twins. Net nonesterified cholesterol hepatic release did not differ with days from parturition (P = .77). There was a net hepatic release of nonesterified cholesterol in the ewes with twins and a net hepatic uptake in the ewes with singles and in nonpregnant ewes (P = .03). There was a net PDV release of NEFA; however, it did not differ with litter size (P = .59) or days from parturition (P = .63). Hepatic NEFA uptake increased with litter size (P = .03) and increased as gestation progressed (P = .006). There was an interaction (P = .04) between litter size and days from parturition for net PDV glycerol release. Net PDV glycerol release in the nonpregnant ewes decreased over time, but release in pregnant ewes tended to increase over time. Hepatic glycerol uptake increased with litter size and increased as gestation progressed. There was a net PDV uptake of triacylglycerol, but it did not differ with litter size (P = .11) or with days from parturition (P = .06). There was a net hepatic release of triacylglycerol, but it did not differ with litter size (P = .59) or with days from parturition (P = .67). Liver utilization of glycerol and NEFA as substrates for metabolism increases as pregnancy progresses. In the nonpregnant ewe, the combined contribution of glycerol and NEFA carbon accounted for 10% of the carbon taken up by the liver, and in ewes pregnant with twins, the combined contribution accounted for 42% of the carbon uptake 19 d before parturition. In conclusion, these data demonstrate NEFA are an important metabolite when determining carbon balance across the liver and their relative contribution to carbon balance increases as pregnancy progresses.
本研究的目的是确定不同胎儿数母羊门静脉引流内脏（PDV）和肝脏的营养物质通量模式。将导管分别置于每只母羊的肝门静脉、肝静脉分支、肠系膜静脉和腹主动脉中。在与公羊接触前，测定血浆流量以及PDV和肝脏的净胆固醇、非酯化脂肪酸（NEFA）和甘油释放量。随后让母羊交配。2只母羊未怀孕，6只母羊产单羔，11只母羊产双羔。在分娩前103、82、61、39、19和6天进行了额外测量。未怀孕母羊的PDV对非酯化胆固醇有净摄取，而产单羔和双羔的母羊有净释放。非酯化胆固醇的肝脏净释放量在分娩前不同天数无差异（P = 0.77）。产双羔母羊的肝脏有非酯化胆固醇的净释放，产单羔母羊和未怀孕母羊的肝脏有净摄取（P = 0.03）。PDV有NEFA的净释放；然而，它在胎次大小（P = 0.59）或分娩前天数方面无差异（P = 0.63）。肝脏对NEFA的摄取量随胎次大小增加（P = 0.03），并随妊娠进展而增加（P = 0.006）。PDV甘油净释放量在胎次大小和分娩前天数之间存在交互作用（P = 0.04）。未怀孕母羊的PDV甘油净释放量随时间减少，但怀孕母羊的释放量随时间有增加趋势。肝脏对甘油的摄取量随胎次大小增加，并随妊娠进展而增加。PDV有三酰甘油的净摄取，但在胎次大小（P = 0.11）或分娩前天数方面无差异（P = 0.06）。肝脏有三酰甘油的净释放，但在胎次大小（P = 0.59）或分娩前天数方面无差异（P = 0.67）。随着妊娠进展，肝脏将甘油和NEFA用作代谢底物的利用率增加。在未怀孕母羊中，甘油和NEFA碳的综合贡献占肝脏摄取碳的1
