Renal renin-angiotensin system activity in naturally reared and cross-fostered spontaneously hypertensive rats

Background: Young (4 week) spontaneously hypertensive rats (SHR) exhibit greater renal responses to angiotensin II (Ang II) than normotensive Wistar Kyoto (WKY) rats. SHR pups cross-fostering to a WKY dam at birth (SHRX) are less sensitive to Ang 11 and have lower adult blood pressure. The aim of this study was to compare renal renin-angiotensin system activity in young naturally reared and cross-fostered SHR pups. Methods: SHR and WKY rats were reared either by their natural mothers or by a foster mother of the opposite strain. At 5, 10, and 15 days of age, renal tissue renin activity and Ang 11 concentration were measured by radioimmunoassay. Renin-secreting cells were identified by in situ hybridization and AT, receptor expression was compared using Western blots. Ang II-mediated cAMP generation was measured in isolated proximal tubules. Results: Tissue renin activity and numbers of renin-secreting cells did not differ, but Ang 11 was higher in SHRX. The AT, receptor expression was significantly lower in SHRX compared with SHR. Basal and Ang II-stimulated cAMP was lower in SHR tubules compared with WKY and SHRX tubules. Conclusions: Cross-fostering reversed the increased renal sensitivity of the SHR to Ang II. These data suggest that renal AT, receptor expression can be manipulated during the postnatal period and that this may affect adult blood pressure. (C) 2003 American Journal of Hypertension, Ltd.