Effect of dietary level of sulfur-containing amino acids on liver drug-metabolizing enzymes, serum cholesterol and urinary ascorbic acid in rats fed PCB

Effect of glucocorticoid treatment on biochemical and hormonal blood parameters in early pregnant gilts

Twenty Polish Landrace gilts were grouped immediately after mating as follows: Experiment I-- Group 1 (5 gilts), control animals and Group 2 (5 gilts), injected i.m. with dexamethasone (30 mg/kg) at 12-h intervals from day 13 to day 22 of pregnancy; Experiment II--Group 3 (5 gilts), injected i.m. with corn oil from day 13 to day 22 of pregnancy and Group 4 (5 gilts), injected i.m. with hydrocortisone acetate (250 mg) at 12-h intervals from day 11 to day 20 of pregnancy. Gilts were placed in metabolic cages on day 7. On days 34-36 of pregnancy gilts were slaughtered and blood samples were collected. Serum was used for analysis of aspartate aminotransferase (S-ASAT), alanine aminotransferase (S-ALAT), alkaline phosphatase (S-ALP), S-cholesterol, S-triglycerides, S-fructosamine, S-urea, S-total protein, and for electrophoretic fractionation of serum proteins, corticosteroid-binding globulin (CBG), cortisol, progesterone, thyroxine (T4) and free T4. There were no significant differences between groups in embryonic survival or in number of viable fetuses after treatment with glucocorticoids. The activity of S-ALP was lower (p < 0.05) in Group 4 than in Group 3 (0.5 vs 1.2 mukat/l). Group 4 had higher (p < 0.05) levels of S-triglycerides (1.17 vs 0.73 mmol/l), S-cholesterol (5.4 vs 2.7 mmol/l), S-total protein (110.5 vs 93.3 g/l), S-albumin (56.3 vs 43.3 g/l) and alpha 2-globulin concentrations (18.0 vs 14.3 g/l) than Group 3. The hydrocortisone-treated gilts had lower (p < 0.05) CBG (6.8 vs 21.3 nmol/l) and beta 1-globulin (3.25 vs 5.0 g/l) concentrations than the oil-treated ones. Concentrations of T4 were lower (p < 0.05) in Groups 2 (61.3 nmo/l) and 4 (49.0 nmol/l) compared with control Groups 1 and 3 (88.2 and 97.0 nmol/l, respectively). Overall, the treatment of early pregnant gilts with hydrocortisone acetate resulted in decreased levels of S-ALP, CBG, beta 1-globulin and T4, and in increased levels of S-cholesterol, S-triglycerides, S-total protein, S-albumin and alpha 2-globulin. The only effect of dexamethasone was a lowering of T4. There were no differences in free T4, S-fructosamine or S-urea between controls and treatments. Furthermore a negative correlation between triglycerides concentrations and the number of embryos (r = -0.76, p < 0.05) was found in control untreated and oil-treated pregnant gilts.

Alteration of serum lipoprotein metabolism by polychlorinated biphenyls and methionine in rats fed a soybean protein diet

The effects of dietary supplementation of methionine to a 20% soybean protein isolate diet on serum lipoprotein profiles and secretion rate of VLDL in rats receiving polychlorinated biphenyls (PCB) were investigated. Serum cholesterol levels were higher in rats fed PCB or a methionine supplement than in controls. The effects of PCB and methionine were synergistic. The feeding of PCB resulted in more cholesterol in all fractions of serum lipoproteins tested, especially HDL (HDL1 and HDL2). Dietary supplementation of methionine primarily increased HDL cholesterol. The elevation of serum lipoprotein cholesterol due to PCB and/or methionine was significant in HDL1, which showed alpha-mobility. These results showed that methionine and PCB significantly influenced HDL metabolism. The secretion rate of VLDL was higher in rats fed PCB than in controls, but the addition of methionine to diets did not affect the secretion rate of VLDL cholesterol. This implies that PCB increased serum cholesterol partly through the stimulation of VLDL cholesterol secretion.

Transport and cellular uptake of polychlorinated biphenyls (PCBs)--II. Changes in vivo in plasma lipoproteins and proteins of pigeons in response to PCBs, and a proposed model for the transport and cellular uptake of PCBs

The complex distribution of polychlorinated biphenyl (PCB) isomers and congeners amongst plasma fractions of the pigeon suggests that the lipid and apolipoprotein components of lipoproteins, as well as plasma proteins, may be important in transporting PCBs to tissues (Borlakoglu et al., Biochem. Pharmac. 40, 265 (1990]. Pigeons were injected with the commercial PCB mixture Aroclor 1254 (1.5 mmol/kg body weight). After 120 hr triacylglycerol-like droplets accumulated in hepatocytes ('fatty liver syndrome'), there was proliferation of the hepatic smooth endoplasmic reticulum, and plasma concentrations of triacylglycerol and total cholesterol increased. This was accompanied by significant decreases in plasma concentrations of total protein, total apolipoproteins of the low density lipoprotein (LDL) and the high density lipoprotein (HDL) fractions, and albumin and by a significant increase in that of urea, indicating increased protein breakdown. These results suggest that Aroclor 1254 increased hepatic lipid synthesis, but decreased hepatic production of albumin and apolipoproteins. This would explain the accumulation of triacylglycerol in the liver and the increase in the proportion of triacylglycerol to apolipoprotein in the total lipoproteins. From the evidence presented, a model is proposed based on the association of PCBs with hydrophobic domains of lipids and proteins for the transport of PCBs by plasma fractions, their uptake into cells and intracellular metabolism, and their accumulation in adipose tissue.