Abstract: Objective To observe changes in surface tension of bronchoalveolar lavage fluids (BALF) in rabbits with
hyperbilirubinemia and the influence of bile diluents and 5 different bile acids on BALF surface tension to provide better
insight into the regulatory role of bile acids on respiratory function. Methods Bronchoalveolar lavage with 0.9% normal saline
was carried out in 30 male New Zealand rabbits and the surface tensions of BALF were measured. The changes in BALF
surface tension was measured in rabbits with hyperbilirubinemia. Different concentrations of bile diluents, normal saline, or
water solutions of 5 bile acids were added into the collected BALF to test their influence on the surface tension of BALF.
Results The BALF from rabbits with hyperbilirubinemia showed a significantly increased surface tension (P<0.05). The bile
diluents (1∶15, 1∶10, and 1∶5) added into the BALF increased the surface tension of the BALF by 21.15%, 26.09%, and 19.64%,
respectively. Among the water solutions of the 5 bile acids, UDCA produced no significant influence on the surface tension of
BALF while CDCA, CA, LCA, and DCA increased the surface tension by 16.10%, 21.66%, 14.21%, and 13.05%, respectively.
Conclusion The surface tension of BALF increases significantly during hyperbilirubinemia. Bile diluents as well as the free bile
acids CDCA, CA, LCA and DCA, but not UDCA, can increase the surface tension of BALF, suggesting that these bile acids may
emulsify pulmonary alveolar surfactants to increase the alveolar surface tension.