Identification of renin in resident alveolar macrophages and monocytes: HPLC and immunohistochemical study

Normal, unstimulated alveolar macrophages (AM) and monocytes (Mo) from both mice and rats have been shown to exhibit an angiotensin-I-forming enzyme. This protease has a similar or identical molecular weight to plasma renin as judged by HPLC analysis. In addition, the enzyme activity could be almost completely inhibited by a specific antibody to pure mouse submaxillary gland renin. This indicates that the angiotensin-I-generating protease in AM and Mo is identical to true renin. These results are in accordance with those of immunocytochemical studies, since the cells sharing immunoreactive renin are macrophages and monocytes. The low percentage of renin positive cells may indicate a functionally different and probably distinct subpopulation of AM and Mo. The presence of renin and angiotensins and angiotensin-I-converting enzyme in normal macrophages and monocytes seems to be common. Hence, the data presented raise the possibility that an intracellular renin-angiotensin system may infact exist in a certain subpopulation(s) of normal macrophages and monocytes.

A mouse gene family associated with a major submaxillary-gland glycoprotein

A gene family encoding msp36 (mouse submaxillary protein 36), a major product of the mouse submaxillary gland, was shown by Southern analysis and genomic cloning to contain approx. 10 related genes. Heteroduplex mapping has elucidated the structure of one of the genes. Close physical linkage of four of the genes in this family has been demonstrated by the use of specific oligonucleotide probes.