Carbohydrate content of apolipoprotein B-48 from rat chylomicrons of varying density.

Monosaccharide composition was determined in apolipoprotein B-48 (apoB) of chylomicrons of rat mesenteric lymph. Chylomicrons were separated into three fractions based on density. Triglyceride and apolipoprotein content were determined in each. ApoB was isolated and quantified using precipitation with isopropanol. Chylomicrons were collected in lymph under normal conditions, and with Poloxalene 2930 when chylomicron secretion was inhibited. Most of the triglyceride was carried in the least dense fraction, while the highest apoB content was in the most dense fraction under normal conditions. Mannose and galactosamine contents of apoB were similar in all fractions while contents of both glucosamine and galactose were highest in the least dense fraction. When chylomicron secretion was inhibited by Poloxalene, the amount of triglyceride recovered in the least dense fraction was significantly reduced. Despite the inhibition of lipid transport in the least dense fraction of chylomicrons by Poloxalene, there was little change in apoB recoveries and in the relative content of various monosaccharides in the apoB from each of the three fractions as compared to results obtained during lipid absorption under normal conditions. In conclusion, carbohydrate composition of apoB of chylomicrons is heterogeneous and varies with chylomicron density.

Alterations of secretory pattern of intestinal lipoproteins by the benzoyl ester derivative of poloxalene surfactant (BEP).

Hydrophobic surfactant BEP was administered intraduodenally as part of lipid emulsion to rats with cannulated mesenteric lymphatic duct. The effect on the size and composition of intestinal triglyceride-rich lipoproteins (TRLp) was assessed by comparing the results with those obtained during infusion of the lipid emulsion alone. Administration of BEP decreased intestinal capacity to transport triglyceride and cholesterol in large TRLp, SF greater than 2000, and resulted in a significant reduction of total triglyceride in lymph. Non-apoB apolipoproteins decreased significantly in large and increased in small TRLp without appreciable change in total content. Contrary to these findings total apoB protein content increased significantly, primarily due to an increase in small TRLp. Changes in lipid and protein content of apolipoproteins produced by BEP resulted in increased ratios of apolipoproteins to lipids in TRLp. It was therefore concluded that inhibition of lipid transport by BEP was not a result of apolipoprotein deficiency. Discontinuation of BEP administration resulted in a prompt recovery of the intestinal lipid transport system.

Hydrophobic surfactant effects on aortic cholesterol accumulation and atherosclerosis in hypercholesterolemic rabbits.

Studies were performed in hypercholesterolemic rabbits to determine whether the hydrophobic surfactant, Poloxalene 2930 (Pol), is of benefit under these conditions. Lipoprotein analyses plus chemical and morphologic studies of the aorta were performed to evaluate the results. In one study, rabbits were made hypercholesterolemic by dietary means and then divided into two groups and given a cholesterol-free diet with one group additionally given Pol with treatment continued for 10 weeks. Pol treatment resulted in less atherosclerosis but the mechanism for this effect was not apparent from lipoprotein analysis. In the other study 3 groups of rabbits were given a cholesterol-rich diet for 16 weeks. Two groups received Pol supplement with one of these groups receiving a dose that was too small to prevent hypercholesterolemia. In this group plus the group on diet alone comparable degrees of hypercholesterolemia were maintained throughout the study. Lipoprotein abnormalities were similar in these two groups except that those on Pol had a more normal cholesterol to apolipoprotein B ratio. The amount of atherosclerosis in both groups was mild but aortic cholesterol content was much less for the Pol group. It is concluded that Pol limits cholesterol accumulation in the aortic wall of hypercholesterolemic rabbits and can retard the development of atherosclerosis.

Activity of some hydrolases in mice with transplantable lymphatic leukemia P 388.

Mice--BDF, hybrides, males aged 3 months were injected intraperitoneally with 10(4) lymphatic leukemia cells P 388. The mice were killed by bleeding after 2.5 and 10 days after the injection. Gamma-glutamyltransferase (GGT), leucylaminopeptidase (LAP) and cobalt activated acylase activity were determined in the serum of the mice. The inner organs of the animals were verified histopathologically. A statistically significant increase in the activity of the examined enzymes was observed together with the development of transplantable leukemia. These enzymes can be helpful in early monitoring of lymphatic leukemia P 388 in mice--as markers of cancer growth.

Inhibition of lipid absorption by non-ionic hydrophobic surfactant Pluronic L-81, and its benzoyl esters.

The benzoyl ester of Pluronic L-81 (BEP) has been purified on an aluminium oxide column and fractionated on the basis of its mobility characteristics into three fractions, BEP I, II and III. Absorption studies were made with rats fed by gavage a lipid preparation containing [14C]triolein and [3H]cholesterol (control animals) and one of the fractions or Pluronic L-81, or crude BEP. After 4 h the amount of lipid absorbed and transported was calculated as the difference between the dose fed and the amount of lipid recovered from the gastric and intestinal luminal contents and intestinal mucosa. Pluronic L-81 was the most effective in inhibiting absorption of triolein but it did not inhibit absorption of cholesterol. BEP-II was almost as effective in inhibiting the absorption of triolein and also inhibited absorption of cholesterol. Crude BEP was less effective and BEP-I and III had only limited activity. Inhibition of triolein absorption by Pluronic L-81 may be partly related to its delaying action on gastric emptying. As purified BEP preparations had practically no effect on gastric emptying, their inhibiting activity involved intestinal mechanisms of lipid absorption.

Determination of amylase by measurement of enzymatic activity and by enzyme immunoassay and radioimmunoassay.

Alpha-amylase content was determined by enzyme immunoassay and radioimmunoassay and enzyme activity by enzymatic test in some pig tissues and serum during ontogenetic development. Among the studied organs, the highest enzyme content and activity were found in the pancreas. In this organ, amylase ratio in fetuses, newborns and adults was 1:13:1500. The ratio of the adult amylase content in pancreas, parotid gland and kidney was 4000:5:1, respectively. Close correlation was shown between the results obtained with the immunological and enzymatic methods.

Enzyme immunoassay for alpha-amylase.

A sensitive sandwich enzyme immunoassay has been developed for quantitation of alpha-amylase in pig pancreas. The alpha-amylase-antibody conjugate was prepared from horseradish peroxidase coupled with antibodies to hog pancreas alpha-amylase. With this method the measuring range is 1-10 ng/ml and the detection limit is 0.2 ng/ml. The amount of pig pancreatic amylase was measured to be 6.21 +/- 2.05 mg/g of tissue. The enzymatic activity determination and immunoassay were compared in the material studied.

Acylases in plasma of hamsters with experimental hepatitis.

After the administration of D-galactosamine to golden Syrian hamsters, a rapid but short-lived increase in acylase I and cobalt-activated (AA-Co) activity was noted in the blood plasma, but not in the liver. In the plasma of control hamsters, only form 2 AA-Co was identified, but during experimental hepatitis, the appearance of form 1 was observed. Only form 2 hamster enzyme is strongly inhibited by alpha-hydroxyisocaproil-tyrosine and reacts with antihuman form 2 antibody.

Molecular forms of cobalt-activated acylase in human tissues and serum of patients with viral hepatitis.

Two molecular forms of cobalt-activated acylase present in human tissues and one or three in sera of patients with viral hepatitis were noted. They have different substrate specificity. Only form 2 is strongly inhibited by alpha-hydroxyisocaproyl-tyrosine and -phenylalanine. Electrophoretic migrations of all enzyme forms are different from those of aminoacylase. Immunoglobulin antiform 2 of the acylase does not precipitate other forms of cobalt-activated acylase or aminoacylase.

Purification of cobalt-activated acylase by affinity chromatography.

alpha-Hydroxyisocaproyltyrosine (HyIc-Tyr-OH), a potent competitive inhibitor of the cobalt-activated acylase form 2, was synthesized. Its derivative, alpha-aminopentyl-HyIc-Tyr-OEt was coupled to cyanogen bromide-activated Sepharose 4B and was used for about 100-fold purification of the acylase from human liver by affinity chromatography. The preparation obtained did not show aminoacylase, aspartyl acylase or alanylarylamidase activities. The same chromatographic method was also applied to isolate form 2 of the serum acylase from patients with viral hepatitis and guinea pig placenta.

Activity and polymorphism of the cobalt-activated acylase in tissues of rodents during development.

The activity of cobalt-activated acylase, measured towards N-chloroacetyl- and N-butyryl-gamma-L-glutamyl-beta-naphthylamide, was found in all tissues of the adult animals. In the kidney, liver and small intestine of adult guinea-pig and rat two fractions differing in electrophoretic mobility (fractions 1 and 2) were present. The early foetus contained fraction 2, sometimes accompanied by fraction 3 which later disappeared; on further development of the foetus, fraction 1 appeared. Fraction 1 was distinctly activated by cobalt ions; fractions 2 and 3 were strongly inhibited by deaminated leucylphenylalanine. In the guinea-pig, the molecular weight of the three fractions ranged from 43000 to 59000.

Cobalt-activated acylase in serum of patients with viral hepatitis.

Newly synthesized and non-toxic acyl derivatives of p-aminobenzoic acid were used as substrates indiagnostic kit for assay of cobalt-activated acylase activity. The enzyme activity, in serum of patients with viral hepatitis, depends on time, type and treatment of the disease and also on age and sex of patients. The presence of HBs antigen has no influence on it. In the patient sera 1-3 molecular forms of the enzyme were found but in the liver of healthy or sick individuals two forms were noted. Using alpha-hydroxy-isocaproyl-tyrosine covalently coupled to Sepharose 4B as a bioadsorbent; the form 2 of acylase from human liver was isolated and separated from the form 1, aminoacylase and aspartyl acylase. Specific immunoglobulins anti-form 2 does not react with other forms of the enzyme either in serum or in the liver.