Rat sn-glycerol-3-phosphate acyltransferase: molecular cloning and characterization of the cDNA and expressed protein.

Rat mitochondrial glycerol-3-phosphate acyltransferase (GPAT) cDNA was cloned and characterized. We identified a cDNA containing an open reading frame of 828 amino acids that had an 89% homology with the coding region of the previously characterized mouse mitochondrial GPAT and a predicted amino acid sequence that was 96% identical. The rat 5' UTR was only 159 nucleotides, in contrast to the 926 nucleotide 5' UTR of the mouse cDNA and had an internal deletion of 167 nucleotides. GPAT was expressed in Sf21 insect cells, and specific inhibitors strongly suggest that, like the Escherichia coli GPAT, the recombinant mitochondrial GPAT and the mitochondrial GPAT isoform in rat liver contain critical serine, histidine, and arginine residues.

Effect of black pepper and piperine on bile secretion and composition in rats.

The influence of black pepper (Piper nigrum L.) and its active principle, piperine on the secretion and composition of bile was investigated in the rat. They were administered by gavage (black pepper at 250 or 500 mg and piperine at 12.5 or 25 mg/kg body wt.) or fed in the diet for 4 weeks (black pepper at 0.2 and 0.4%, piperine at 0.01 and 0.02%). The lower dose by gavage of black pepper caused an increase in bile solids while with other treatments bile secretion or dry matter in bile was not changed. Dietary feeding of black pepper caused an increase in bile flow with a concomitant decrease in bile solids -- a hydrocholagoguic effect. Cholesterol and bile acid output were not affected by black pepper or piperine at either level irrespective of the mode of administration; in contrast, the secretion of uronic acids in bile was enhanced by both levels of pepper as also of piperine indicating possible excretion of some of the components of black pepper or of piperine as glucuronides.