The Effect of Diet on Liver Cholesterol in Chickens

Sperry, Warren M.; Stoyanoff, V.A.

doi:10.1093/jn/9.2.157

Cited by 5 publications

(3 citation statements)

References 8 publications

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“…On the other hand, if experimental co~ditions require the ina~tivat~on of the enzyme withou~hangi~g normal plasma c~~ditions, heating at 56-60°C f~O min. is quite effectivé (215). LCAT is inactivated bpt the capacity of the,plasma lipoproteins to act as subsFrates 1s unaltered (216).…”

Section: Mu1der and Van Deenen Have Demonstrated The Presence Of Lysomentioning

confidence: 99%

Some Characteristics of the Exchange of Lecithin between Rabbit Erythrocytes and Serum

Smith¹,

Rubinstein²

1974

Can. J. Biochem.

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The exchange of lecithin between rabbit erythrocytes and serum has been investigated. The erythrocyte lecithin was labelled in vivo by administration of Na332PO4, which resulted in the acquisition of [32PJlecithin by the cells primarily by exchange, and in vitro by esterification with [3H]palmitate, [14C]linoleate, or [14C]linolenate. The rate of exchange of erythrocyte [32PJ-phospholipids was independent of specific serum lipoprotein fractions, but was related to the serum phospholipid concentration. Analysis of the erythrocyte inward and outward exchange rates of [32P]lecithin revealed that only 55% of the cellular lecithin pool takes part in the exchange. A similar conclusion can be reached by comparison of the fractional exchange rates of the acyl- and 32P-labelled erythrocyte lecithin, or by comparison of the ratio of acyl to 32P radioactivity of the erythrocyte lecithin with the ratio found in the serum after exchange. These data indicated that the proportion of the acyl-labelled erythrocyte lecithin pool (± S.E.M.) capable of exchange was 53 ± 5%, 64 ± 12%, and 95 ± 6%, when esterified with [14C]linoleate, [3H]palmitate, and [14C]linolenate, respectively. The differences in the proportion of the acyl-labelled erythrocyte lecithin pool undergoing exchange could not be attributed to the preferential exchange of a particular molecular species of lecithin, although the tetraenoic lecithin did exchange to a relatively greater degree. This suggests that cellular lecithin formed by esterification of linolenate is found only in the portion of the pool available for exchange, whereas that formed by esterification of linoleate and probably palmitate is distributed throughout the entire lecithin pool. The fractional exchange rate of [32P]lecithin of isolated erythrocyte membranes was 3 times that of the lecithin of intact cells. However, the difference in fractional exchange rates between [3H]palmityl-lecithin or [14C]linoleyl-lecithin and [32P]lecithin is reversed in the membranes. These observations suggest that a portion of the total cellular lecithin pool becomes available for exchange only upon disruption of the erythrocyte, and may be located in a relatively inaccessible portion of the membrane such as the inner surface.

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Section: Mu1der and Van Deenen Have Demonstrated The Presence Of Lysomentioning

confidence: 99%

Some Characteristics of the Exchange of Lecithin between Rabbit Erythrocytes and Serum

Smith¹,

Rubinstein²

1974

Can. J. Biochem.

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“…Cholesterol-esterifying activities of the serum, obtained a t weekly intervals, are given in Table 11. The significance of this reported decrease is uncertain because the diet employed contained bile salts in addition to cholesterol; bile salts have been shown (10,11) to be inhibitors of the cholesterol-esterifying enzyme in plasma. A highly significant positive correlation has been demonstrated in humans (8) between the concentration of free cholesterol in plasma and the rate of cholesterol esterification in plasma.…”

Section: (34)mentioning

confidence: 99%

Dietary Cholesterol and Serum Cholesterol-Esterifying Activity in Rabbits

Wells¹,

Rongone²

1969

Experimental Biology and Medicine

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1) was the first to demonstrate that blood serum contains a cholesterolesterifying enzyme. I t is a liver produced ( 2 ) acyltransferase and the P-position of lecithin is the source of the required acyl groupsThe activity in plasma of this enzyme, phosphatide: chloesterol fatty acid transferase, is increased in essential fatty acid (S), pantothenic acid and choline deficient rats (6) and decreased in inositol deficient rats (6). In these vitamin deficiency states, the increased activity of the enzyme is accompanied in male rats by increased concentrations of cholesterol esters in the tissues (6).These observations suggest that the cholesterol-esterifying enzyme in plasma may serve an important role in the process of cholesterol ester deposition in the tissues. We have sought additional evidence for this concept by determining the change of activity of the enzyme in the serum of cholesterol-fed rabbits. Increased enzyme activity was observed accompanied by increased concentrations of cholesterol esters in some of the tissues.Methods. Twelve rabbits, equally divided as to sex, with body weights in the range 2.5-3.0 kg were obtained from a commercial supplier. Two of the animals were used for *Supported in part by Grant (P-365 A) from the 1 Career Development Awardee (5-KO3-AM25401). (3,4). American Cancer Society to E. L. R.the determination of the normal tissue cholesterol concentrations. Blood samples were obtained from an ear vein of each of the remaining animals at the start of the experiment and 5 days later. During this time the animals were fed a pelleted rabbit chow. Sera from these blood samples were analyzed to obtain control levels of cholesterol and cholesterol-esteri f ying activity .After the second blood samples were obtained, the rabbits were given the pelleted chow onto which cholesterol had been deposited from an ether solution to give a cholesterol concentration of 0.7 g/lOO g of diet. The animals were continued on this diet for 6 weeks and blood samples were obtained, as above, at weekly intervals and the sera were analyzed for cholesterol and cholesterol-esterifying activity. At the end of the cholesterol feeding period, the animals were anesthetized, killed by exsanguination and samples of tissues were removed and frozen on dry ice. They were subsequently analyzed for their contents of cholesterol.The activity of the cholesterol-esterifying enzyme in 0.50 ml of each serum sample was determined as previously described (6) using as substrate 2.0 ml of normal, heated rabbit serum containing cholesterol-1 C~-~H . '~ Enzyme activities in the fresh experimental sera were expressed as dpm converted to cholesterol

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“…It has long been known that enzymically catalysed synthesis and hydrolysis of cholesterol esters occurs in the presence of certain tissues (Kondo, 1910a, b;Schultz, 1912;Cytronberg, 1912;Gardner & Lander, 1913;Mueller, 1916a, b;Porter, 1916;Nomura, 1924a, b;Shope, 1928;Nedswedski, 1935Nedswedski, , 1936Klein, 1939;Sperry, 1935;Sperry & Stoyanoff, 1937, 1938. The most extensive recent studies, initiated with the enzyme from pancreas, are those of Yamamoto, Goldstein & Treadwell (1949) and Swell & Treadwell (1950a), who stressed the importance of stable emulsions of cholesterol and cholesterol esters and described their preparation.…”

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confidence: 99%