Expression and distribution of NOS1 and NOS3 in the myocardium of angiotensin II-infused rats

Studies have indicated a complex functional interaction between angiotensin (Ang) II. and NO in the heart. The purpose of the present study was to exa mine the protein expression and tissue distribution of NO synthases 1 (NOS1 ) and 3 (NOS3) in the myocardium of rats that underwent continuous infusion of Ang II. at 2 different rates (10 and 40 ng . kg(-1) . min(-1)) for 6 da ys. Mean arterial pressure increased by approximate to 15 mm Hg in rats inf used with Ang II at 40 ng . kg(-1) . min(-1), but it remained close to the values observed in saline-infused rats (approximate to 110 mm Hg) when Ang II was infused at 10 ng . kg(-1) . min(-1). The protein expression of a 160 -kDa NOS1 and a 135-kDa NOS3 were found to increase (approximate to 200%) i n the myocardium of rats infused with both subpressor and presser doses of Ang II. Immunohistochemistry studies showed that NOS1 and NOS3 are differen tially expressed in myocardial cells. NOS1 was detected in cardiac myocytes and in smooth muscle cells of small and large coronary arteries, whereas N OS3 was detected in the endothelium and in perivascular and interstitial ti ssues, but NOS3 was not detected in cardiac or smooth muscle cells. Ang II infusion enhanced the tissue immunoreactivity of both isoforms in their spe cific locations but did not change the distribution throughout the myocardi um. Myocardium staining with anti-angiotensin type 1 (AT(1)) receptor antib ody indicated that AT(1) receptor is expressed in cardiac myocytes, coronar y smooth muscle cells, and interstitial and perivascular tissues. Ang II in fusion did not change the protein expression and distribution of AT(1) rece ptor in the myocardium, These results indicate that long-term increases in the circulating levels of Ang II modulate the protein expression of NOS1 an d NOS3 and, consequently, the function of the local myocardial NO system.