Plasma Tributyrinase in the Neonatal Period IncIud ng a Micromodiflcation of a Tlirimetrk Method

HE PRESENT s’ru was suggested by the lack of data on plasma tnbutyrinase (lipase) activity in the neonatal period. Titrimetric methods are not practical for small amounts of blood and it was found necessary to adapt the method of Goldstein et al. (1) to an electrometric procedure. Such a modification reduced to %o the amount of plasma and reagents needed in the titrimetric method. Troescher and Norris (2) determined blood esterase electrometrically by the addition of oxalated blood to a 0.15 M phosphate buffer at pH 8.9 with ethyl butyrate as substrate. It has since been shown that tributyrin substrate results in appreciably higher enzymatic activity (3) than does ethyl butyrate. The preparation of our substrate was identical with that described in Standard Methods of Clinical Chemistry (4) with the omission of sodium choleate (1). The modified electrometric procedure reported here has been used in our laboratory for routine clinical determinations of tributyrinase and found satisfactory.