Immunohistochemical localization of renin, NO synthase-1, and cyclooxygenase-2 in rodent kidney.

The renin-angiotensin system (RAS) and tubuloglomerular feedback (TGF) are central to the maintenance of blood pressure and body fluid composition. Renin, NO synthase-1 (NOS-1), and cyclooxygenase-2 (COX-2) are key regulators of the RAS and TGF. In the present study, to investigate species-specific differences in the RAS and TGF, we immunohistochemically and morphometrically investigated the localization of renin, NOS-1, and COX-2 in the kidneys of various laboratory rodents and comparing males with females (DBA/2Cr mice, F344/N rats, Syrian hamsters, MON/JmsGbs gerbils and Hartley guinea pigs). In all animals, renin-positive immunoreactions were observed in the vascular walls of afferent arterioles. Renin immunoreactions appeared to be more widely distributed in mice. Mice had a greater number of renin-positive arterioles than other species. NOS-1-positive reactions were detected in the macula densa (MD) of all animals. Mice had the greatest number of NOS-1-positive MD cells. In addition to NOS-1-positive reactions, COX-2-positive reactions were observed in the MD of mice, rats, hamsters and gerbils. Interestingly, guinea pigs had no COX-2-positive MD cells. Rats had the greatest number of COX-2-positive MD cells. In nephron segments excluding the MD, the immunohistochemical localization of NOS-1 and COX-2 differed markedly among not only species but also sexes within the same species. In conclusion, we determined that localization of renin, NOS-1, and COX-2 showed large species- and sex-related differences. These data suggest that the regulation mechanisms of the RAS and TGF via renin, NOS-1, and COX-2 differ among rodents.