- Lack of biliary lipid excretion in the little skate, Raja erinacea, indicates the absence of functional Mdr2, Abcg5, and Abcg8 transporters. Elferink, R.P., Ottenhoff, R., Fricker, G., Seward, D.J., Ballatori, N., Boyer, J. Am. J. Physiol. Gastrointest. Liver Physiol. (2004)