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Ancestrally, oryzomyine rodents have a sylvan habit, but some species have colonized the semi-arid Brazilian Caatinga. Therefore, the clade provides a suitable model for studying adaptation to such environments within a phylogenetic framework. We investigated physiological responses to short-term water deprivation in two oryzomyine rodents kept in captivity. Oligoryzomys nigripes (Olfers, 1818), a small-bodied rodent, occupies the Caatinga, whereas Nectomys squamipes (Brants, 1827), which is larger and semi-aquatic, lives in moist habitats outside this region. Measurements were also carried out in three additional related species of intermediate body size. Neither O. nigripes nor N. squamipes displays exceptional ability to conserve water, and this condition appears to be plesiomorphic for the clade. The results for O. nigripes, such as the great absolute water intake and the high ratio of water ingested to urine voided, probably derive from allometric specializations correlated with its small body size and greater evaporative water loss. In N. squamipes, low urine osmolality and a reduction of food intake during water deprivation may be related to its semi-aquatic lifestyle. Therefore, the Oryzomyini exemplify Neotropical rodents that can occupy semi-arid environments with no remarkable physiological adaptation for water conservation.

The increased intrarenal renin‐angiotensin system (RAS) activity contributes to diabetic nephropathy. A high glucose (HG) extracellular concentration (EC) induces activation of RAS in mesangial cells. However, this relationship in the collecting duct was not studied yet. The aim of this study was to evaluate the modulation of RAS in collecting duct cells (mIMCD‐3) induced by HG concentration. At the subconfluence (80%) the cells were divided into three groups: Normal Glucose (5 mM D‐glucose, NG), High Glucose (30 mM D‐glucose, HG) or Mannitol (30 mM, M) and were maintained for 48h in these medium. The ACE and ACE2 activities were measured using a fluorimetric assay and the cellular localization of ACE was examined by immunofluorescence. The RAS components were analyzed by western blotting and HPLC‐UV. Our results showed that ACE activity was significantly lower at intracellular (IC) (27%) and EC (22%) content in the cells of HG group when compared with NG and M. The IC activity of ACE2 was higher in HG and M (68 and 73%, respectively). The protein expression of ACE (69kDa) was lower in groups HG and M. The renin expression was higher in HG when compared to NG and M, with no changes in in other proteins of RAS. The ANG I, ANG II and ANG 1‐7 were higher in HG compared to NG and M, both in IC and in EC content. The ACE migrated to the cell nucleus in the HG mIMCD‐3 cells, what could act like a transcription factor. We also suggest that the HG concentration activates a compensation mechanism avoiding the deleterious effects of ANG II. Financial support: CAPES, FAPESP, MACKPESQUISA.