RENIN IS EXPRESSED IN RAT MACROPHAGE MONOCYTE CELLS

The cardiac renin-angiotensin system has been suggested to be involved in various pathological conditions, including hypertrophy and remodel ing. However, direct evidence that the renin synthesized in situ is re ally involved in the putative angiotensin II generation is still lacki ng because of the relatively low abundance of renin mRNA in cardiac ti ssues. We evaluated renin mRNA expression levels in the ventricles und er various pathological conditions and found that renin gene expressio n was markedly increased in the ventricles of isoproterenol-treated ra ts. Renin mRNA expression levels in the ventricles of rats that had be en injected with isoproterenol (150 mg/kg SC) were transiently and mar kedly increased to 6-, 90-, and 4-fold compared with control expressio n levels at 24, 72, and 120 hours, respectively, after isoproterenol a dministration. Immunohistochemical analysis revealed that some of the OX-42-positive macrophage/monocyte cells had a reninlike immunoreactiv ity. An in vitro experiment indicated that rat peritoneal macrophage/m onocyte cells expressed renin mRNA in abundance. The present study con firmed that a subpopulation of macrophage/monocyte cells could express renin. Macrophage/monocyte cells may be a source of tissue renin in s ome pathological conditions.