BREAST GUT CONNECTION - ORIGIN OF CHENODEOXYCHOLIC ACID IN BREAST CYST FLUID

The notion that a breast-gut connection might modulate the microenviro nment of breast tissue was supported by the finding that breast cyst f luid contains bile acids that are characteristically found in the inte stines. To establish that the gut, rather than circulating steroid pre cursors, is the source of bile acids in breast cyst fluid, we gave two patients deuterium-labelled chenodeoxycholic acid (three 200 mg doses by mouth), starting 9 days before aspiration of breast cysts. The che nodeoxycholic acid concentration of seven samples of aspirated cyst fl uid ranged from 42 to 94 mu mol/L. The corresponding plasma concentrat ions of chenodeoxycholic acid on the same day were 0.80 and 2.90 mu mo l/L, of which the labelled compound comprised 13.0% (0.38 mu mol/L) an d 28.2% (0.23 mu mol/L). The deuterated chenodeoxycholic acid concentr ations in cyst fluid were 1.8 and 1.4 mu mol/L in two samples from pat ient 1 and 4.7 mu mol/L in patient 2; these values are equivalent to 1 1-17% of the plasma concentrations. This study shows that intestinal b ile acids rapidly gain access to cyst fluid. Further studies should in vestigate the mechanisms that govern the exchange processes and the ma intenance of the high cyst fluid to plasma concentration gradients, an d the biological half-lives of individual constituents.