The gastrointestinal tract: an underestimated organ as demonstrated in an experimental LVAD pig model.

BACKGROUND: Although hemodynamic stability and renal function are important and are monitored closely in patients with implanted left ventricular assist devices (LVAD), the gastrointestinal tract may be underestimated in the early postoperative period with regard to adequate perfusion. We investigated renal, intestinal, and whole body metabolic changes in response to variations in LVAD flow and inspired oxygen concentration (FiO2). METHODS: Left ventricular assist devices were implanted in 10 adult pigs (weight, 55 +/- 1.76 kg). Renal vein (RV), superior mesenteric vein (SMV), and pulmonary artery (PA) blood oxygen saturation and lactate concentration were measured and used as tissue perfusion markers. These measurements were made at baseline and after changes in LVAD flow or FiO2. RESULTS: Oxygen saturation in the PA, SMV, and RV decreased significantly after a reduction in LVAD flow (P < 0.05), with a greater reduction in the SMV than in the PA and RV (p < 0.05 at LVAD flow 3.5L/min; p < 0.01 at LVAD flow 2.0 and 1.0 L/min). The lactate concentration in the PA and SMV increased significantly (p < 0.01) with decreased flow, with a greater increase in the SMV than in the PA (p< 0.05), whereas it remained unchanged in the RV. Oxygen saturation in the PA, SMV, and RV decreased significantly after a reduction in FiO2 (p < 0.05). Lactate concentration in the PA, SMV, and RV increased significantly at FiO2 of 0.10 (p < 0.05). Lactate concentration in the PA and SMV was significantly higher than that in the RV at Fi)2 of 0.10 (p < 0.01). CONCLUSIONS: The results show that the gastrointestinal tract is at high risk during low perfusion or low FiO2, whereas the kidneys' metabolic function appears to be less disturbed. In clinical practice, this emphasizes the need to ensure adequate blood flow and respiratory function, especially after extubation, in patients with implanted LVAD. This might avoid intestinal ischemia and subsequent endotoxemia. Gastrointestinal tonometry may help in the assessment of intestinal perfusion.

Effect of chronic glucagon administration on lipoprotein composition in normally fed, fasted and cholesterol-fed rats.

Male adult Wistar rats received daily (at 9 a.m. and 5 p.m.) 10 micrograms of zinc-protamine glucagon by subcutaneous injection for 8 days. Plasma cholesterol levels were decreased by 36% in fed rats, 33% in cholesterol-fed rats and by 55% in fasted rats. Lipoproteins were separated into 22 fractions by ultracentrifugation using a density gradient. Glucagon administration decreased the cholesterol content in all lipoproteins except low density lipoprotein (LDL1) (1.006-1.040) and very low density lipoprotein (VLDL) from cholesterol-fed rats. The main decrease (-57 to -81%) was observed in 1.050-1.100 g/mL lipoproteins (LDL2 and HDL2), which contained a large amount of apo E, while HDL3 cholesterol was not affected. Triacylglycerol levels were decreased only in chylomicrons and VLDL (-70%) of fed and cholesterol-fed rats, while plasma and lipoprotein triacylglycerol levels were not changed in fasted rats treated with glucagon. In normally fed rats glucagon administration increased by 42% the fractional catabolic rate of [125I]HDL2 while the absolute catabolic rate appeared to be unchanged. Glucagon seems to be a potent hypolipidemic agent affecting mainly the apo E-rich lipoproteins. Its chronic administration limits lipoprotein accumulation which occurs upon cholesterol feeding.

Effect of chronic glucagon administration on the metabolism of triacylglycerol-rich lipoproteins in rats fed a high sucrose diet.

Male adult Wistar rats were fed a semipurified diet rich in sucrose (53 g/100 g diet). The effects of chronic glucagon administration (20 micrograms.day-1.rat-1, for 21 d) were studied on plasma lipid levels, triacylglycerol secretion rates and fractional catabolic rates determined by the intravenous fat tolerance test. Triacylglycerol secretion rates of plasma, chylomicron and very low density lipoprotein (VLDL) were measured by using the Triton WR 1339 method. In both fasting and postprandial states, the different rates were not significantly modified by glucagon treatment. However, in the treated animals, significantly decreased triacylglycerol concentrations were observed in plasma and VLDL during fasting (-41 and -46%, respectively) and also in chylomicrons in the postprandial state (-37%) relative to control animals. These data could be accounted for by an increased removal rate of triacylglycerol-rich lipoprotein. The estimated values of fractional rate constants (Triton WR 1339 experiment) were increased for VLDL (+62%) in the fasting state and for chylomicrons (+104%) in the postprandial state. Similarly, the fractional catabolic rate determined with the intravenous fat tolerance test (Intralipid, Kabivitrum, Sweden) was increased 49% by glucagon treatment, suggesting an effect of glucagon on the catabolism of triacylglycerol-rich lipoproteins. Glucagon treatment did not modify the composition of VLDL obtained 60 min after Triton WR 1339 injection, except that in the fasting state apo B100 proportions and concentrations increased, suggesting a specific effect on the hepatic secretion of apo B100 VLDL.

Particular aspects of thyroid function development in the postnatal rat with special reference to interrelationships between mother and young.

Previous data have demonstrated that thyroid gland thyroxine secretion rate in suckling rats is high and correlated with the hormonal needs of the young. Non-hormonal iodine metabolism is more elevated in the young than in the adult. The object of the present work was to measure rates of iodine transfer in 10-day old families of rats equilibrated with 125I or not. Reciprocal iodine exchange between mother and young occurred in such a way that the dam recovered about 60 p. 100 of the iodine lost in the milk. Moreover, a large store of extrathyroidal iodine was constituted in the young, particularly in the pelt.