p.53 IN VITRO HYDROLYSIS OF MCT RELATIVE TO LCT IS FAVORED AT PHYSIOLOGICAL pH AND IN THE

'RESENCE OF HUMAN PLASMA IN BOTH MIXED AND BLENDED MCT-LCT EMULSIONS. N.SATO, G. Neeser, Y.A. Carpentier, J.M. Kinney, R.J. Deckelbaum. Department of Pediatrics, Columbia University, New York, New York.

We previously reported in Tris buffer-albumin (Tris-A) incubations that MCT and total free fatty acid (FFA) release is optimal in blended emulsions of MCT/LCT and not in mix- tures of pure MCT emulsion plus pure LCT emulsion. We questioned if this preference for MCT hydrolysis in blended vs. 3H-octanoate labelled MCT and

mixed emulsions occurs in human plasma at physiological pH, 14C-palmit ate labelled LCT were emulsified into the same

particles (blended MCT/LCT) or mixed as separate pure emulsion particles (mixed MCT+LCT). Using double radiolabel methodologies ve compared in vitro hydrolysis of MCT and LCT by purified lipoprotein lipases at different ratios - 50:50 or 70:30 MCT:LCT by weight - in Tris-A or human plasma. In Tris-A at pH 8.5, the pH optimum for lipase, total FFA rel- ease was highest in blended MCT/LCT emulsions compared to mixed MCT+LCT at both mixing ratios. The advantage for blended emulsions was retained at pH 7.4 but to a lesser degree. Blended MCT/LCT emulsion hydrolysis was less sensitive to pH than were mixed MCTfLCT emulsions. The major determinant of total FFA release was the amount of MCT present in the emulsion, so that MCT:LCT mixtures of 70:30 released more total FFA than did 50:50 mixtures on a weight basis. In incubations in human plasma rates of hydro- lysis of both MCT and LCT were lowered regardless of the method of mixing so that total FFA release decreased by l/4 to l/3. Decreases in MCT lipolysis were less than with LCT lipolysis, so that in plasma, MCT lipolysis increased relative to LCT, 1.5 to 2 fold. Plasma substantially decreased differences between blended and mixed emulsions because 3~ relative decreases in LCT hydrolysis in the mixed MCT+LCT emulsions. We conclude that MCT hydrolysis rates are always higher than LCT in blended but not in mixed emul- sions, in Tris-A at ph 8.5, and this advantage towards MCT hydrolysis also occurs in mixed emulsions at pH 7.4. Also, differences in hydrolysis between blended MCT/LCT and mixed MCT+LCT emulsions diminish when they are hydrolyzed in human plasma in vitro.

P.54 fS TPN G?DUCED Lyx RBLATND TO KIND OF FAT BMUISION?D.Bobilewicz,T.Korta, #i,Pertkiewicz,J.Kotlicka.Postgraduate Medical Centre,Medical Academy, darsaw,Poland.

The mechanism of Lpx appearance in response to fat administration in TPN patients with no signs of liver function impairement is not clear.As Lpx consists mainly of phospholipids/Ph/ and nonesterified cholesterol/NE-W/ it can be expected that alteration in serum Ph and NR-CH may result in Lpx formation.

Aim of the study was to compare the Lpx appearance in relation to adminis- tration of 2 different emulsions:Intralipid/Int/ and Lipofundin/Lip/.Inves tigations were carried out in 19 nonjaundiced patients receiving TPN with 50-IOOg of fat and 3,75-'7,5g of Ph per day/g-Lip,10-Int/.Study covered 98 nonseptic days with Lip and 104 with Int.Samples were collected at 3 days intervals.Serum Ph,NECH and Lpx were estimated.

Results:In Lip patients regardless the amount of given Ph no Lpx was fauna In Int group amount of Ph causing Lpx formation showed great individual variations/started from 18g/.In Int Lpx+ group NE-CH was significantly hi- gher than in Int Lpx- and Lip/TO,55 and 50mg/dl respectively/.Serum Ph was ~,;t&lar in all patients/l62-168&dL/.Pk4/NE-CH ratio was lower in Lpx+ group/2,54/comparing to ethers/3,05 in Int Lpx- and 3,24 in Lip/.

Conclusion:Increase of serum NR-CH observed in some patients receiving Int ralipid might be considered a s an essential factor responsible for Lpx formation in course of total pprenteral nutrition.

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