EFFECTS OF GLYCINE AND BOVINE SERUM-ALBUMIN ON INHIBITION OF PROPIONATE METABOLISM IN OVINE HEPATOCYTES CAUSED BY REDUCED PHENOLIC MONOMERS

Hepatocytes isolated from sheep were incubated in the presence of redu ced phenolics and glycine to determine the effects of these compounds on hepatic propionate metabolism in vitro. 3-Phenylpropionic (PPA) or t-cinnamic (CA) acids, but not benzoic (BA) or 3-(4-hydroxyphenyl)prop ionic (40HPPA) acids, decreased conversion of propionate to glucose at .05 mM in the absence of supplemental glycine. At 1.2 mM, all reduced phenolics decreased conversion of propionate to glucose in the absence of supplemental glycine. Addition of glycine to the incubation medium linearly alleviated the inhibition by BA, PPA, or CA, suggesting that physiological glycine concentrations limited alleviation of inhibitio n of propionate metabolism. Hippuric acid production increased as glyc ine concentration increased in the presence of PPA, CA, or 40HPPA. Bov ine serum albumin did not alleviate inhibition of conversion of propio nate to glucose caused by BA, PPA, or CA and slightly alleviated inhib ition caused by 40HPPA (.4 mM). Of the reduced phenolics tested, PPA i s the most likely to inhibit gluconeogenesis from propionate in ovine liver in vivo.