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 reduced phenolics and glycine to determine the effects of these compounds on hepatic propionate metabolism in vitro. 3-Phenyl-propionic (PPA) or t-cinnamic (CA) acids, but not benzoic (BA) or 3-(4-hydroxyphenyl)propionic (4OHPPA) 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 inhibition of propionate metabolism. Hippuric acid production increased as glycine concentration increased in the presence of PPA, CA, or 4OHPPA. Bovine serum albumin did not alleviate inhibition of conversion of propionate to glucose caused by BA, PPA, or CA and slightly alleviated inhibition caused by 4OHPPA (.4 mM). Of the reduced phenolics tested, PPA is the most likely to inhibit gluconeogenesis from propionate in ovine liver in vivo.