Alterations of COX-1, 2 mRNA and Protein Expression in Pregnant Rat Kidney / 대한해부학회지

ABSTRACT

The pregnancy causes the marked changes in maternal renal hemodynamic and volume homeostasis. During pregnancy, renal sodium and water retention result in an expansion of extracellular fluid and plamsma volume. This study was to examine the alteration of expression and localization of COX-1, 2, mRNAs and proteins in the kidneys of non-pregnant (NP) and pregnant rats using RT-PCR, Western blot analysis and immunohistochemistry. Pregnant Sprague-Dawley rats were evaluated on various time sets days 10.5 (P10.5), 12.5 (P12.5), 17.5 (P17.5), and 19.5 (P19.5). In RT-PCR, COX-1 expression was gradually increased from P10.5 to P19.5 compared with NP rat. COX-2 expression was gradually decreased from P10.5 to P17.5 compared with NP rat, but restored NP level at P19.5. In Western blot analysis, COX-1, 2 proteins were detected in ~70, ~72 kDa, respectively. COX-1 expression was gradually increased from P10.5 to P17.5 and peaked at P19.5 compared with NP rat. COX-2 expression of pregnant rats was slightly decreased compared with NP rat. In NP rat, immunoreactivity of COX-1 was detected in entire collecting duct, glomerular epithelium, and medullary interstitial cells. In pregnant rats, the pattern of cellular labeling and signal intensity of COX-1 protein was identical to NP rat, but signal intensity was markedly increased in the inner stripe of outer medulla and inner medulla at P19.5. COX-2 immunoreactivity of NP rat was detected in the cortical thick ascending limb and macula densa. In pregnant rats, the pattern of cellular labeling of COX-2 protein was identical to NP rat, but signal intensity was slightly decreased. These results suggest that the expansion of extracellular fluid volume and water retention may be partly regulated by COX-1 rather than COX-2 during the pregnancy, especially at late stage.