Morphology and cyclooxygenase-2 and renin expression in the kidney of young spontaneously hypertensive rats

The kidneys play an important role in blood pressure regulation under normal and pathological conditions. We examined the histological changes and expression patterns of cyclooxygenase-2, renin, and (pro)renin receptor (PRR) in the renal cortex of prehypertensive spontaneously hypertensive rats (SHRs) and Wistar Kyoto rats (WKYs). Moreover, blood pressure and plasma urea, creatinine, angiotensin II, and angiotensin (1–7) levels were measured. The results showed that both strains had similar blood pressure and plasma urea and creatinine levels. The glomerular area, basement membrane thickness, collagen fiber content, and arterial wall thickness were greater in SHRs than in WKYs. By immunohistochemistry, cyclooxygenase-2 was localized in the macula densa and renal tubules of both strains. In SHRs, cyclooxygenase-2 was detected in a larger number of tubules, and the cortical expression of cyclooxygenase-2 was also increased. In both strains, PRR and renin were localized in the tubular epithelium and juxtaglomerular cells, respectively. In SHRs, PRR immunolocalization was increased in the glomerulus. The cortical expression of immature renin was markedly increased in SHRs compared to that in WKYs, while renin was significantly decreased. These changes were associated with higher plasma angiotensin II levels and lower plasma angiotensin (1–7) levels in SHRs. The results indicate that the kidneys of SHRs showed morphological changes and variations in cortical expression patterns of PRR, cyclooxygenase-2, and renin before the development of hypertension.