Occurrence and determination of a natriuretic hormone, 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman, in rat plasma, urine, and bile.

The occurrence of a new natriuretic hormone, 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman (LLU-alpha, gamma-CEHC) in rat plasma was demonstrated and its concentration was determined using a coupled-column HPLC with a fluorometric derivatization with 4-N,N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazol e (DBD-PZ) followed by O-acetylation. The concentration of LLU-alpha was 328 +/- 113 nM in rat plasma (N = 5). LLU-alpha was found in not only urine, but also bile, suggesting an enterohepatic circulation in body. We also assigned the configuration at C-2 of LLU-alpha in these biological fluids as (S)-form by an HPLC with a chiral column. The LLU-alpha concentration decreased significantly by fasting for 3 days (P < 0.01). These results support the possibility that LLU-alpha is produced from gamma-tocopherol in diet via oxidative metabolism without racemization.