BILE SALT-STIMULATED LIPASE (BSSL) DISTRIBUTION IN RAT, MOUSE AND TRANSGENIC MOUSE EXPRESSING HUMAN BSSL

In some species, including man and mouse, bile salt-stimulated lipase (BSSL) in milk catalyzes the hydrolysis of triacylglycerides into glyc erol and free fatty acids, a reaction that is of particular importance during suckling. The enzyme is also secreted by the pancreas (referre d to as carboxyl-ester hydrolase, CEH). We wished to localize sources and storage sites for BSSL/CEH in rats, in wild-type mice, and in tran sgenic mice producing recombinant human BSSL in milk. Immunoreactivity against several BSSL fragments was strong in the pancreatic acinar ce lls and moderate in the absorptive cells of the small intestine and in salivary duct cells of the mice, as well as in rats. Sections from la ctating mammary glands of mouse, but not rat, also showed immunoreacti vity for BSSL; the signal was strongest in the transgenic mice. Radioa ctive riboprobes for BSSL mRNA hybridized on sections of rat and mouse pancreatic acinar cells, and mouse mammary glands (both wildtype and transgenic). Using RT-PCR, it was possible to amplify BSSL mRNA from w ild-type mouse pancreas and mammary gland, from rat submandibular glan ds, and, in a few cases, from rat liver. In transgenic mice, the BSSL mRNA was highly expressed only in lactating mammary gland, but could b e detected in a few other organs as well.