Codistribution of NOS and caveolin throughout peripheral vasculature and skeletal muscle of hamsters

In isolated cell systems, nitric oxide synthase (NOS) activity is regulated by caveolin (CAV), a resident caveolae coat protein. Because little is kno wn of this interaction in vivo, we tested whether NOS and caveolin are dist ributed together in the intact organism. Using immunohistochemistry, we inv estigated the localization of constitutive neuronal (nNOS) and endothelial (eNOS) enzyme isoforms along with caveolin-1 (CAV-1) and caveolin-3 (CAV-3) throughout the systemic vasculature and peripheral tissues of the hamster. The carotid artery, abdominal aorta, vena cava, femoral artery and vein, f eed artery and collecting vein of the cheek pouch retractor muscle, capilla ries and muscle fibers of retractor and cremaster muscles, and arterioles a nd venules of the cheek pouch were studied. In endothelial cells, eNOS and CAV-1 were present throughout the vasculature, whereas nNOS and CAV-3 were absent except in capillaries, which reacted for nNOS. In smooth muscle cell s, nNOS and CAV-1 were also expressed systemically, whereas eNOS was absent ; CAV-3 was present in the arterial but not the venous vasculature. Both nN OS and CAV-3 were located at the sarcolemma of skeletal muscle fibers, whic h were devoid of eNOS and CAV-1. These immunolabeling patterns suggest func tional interactions between eNOS and CAV-1 throughout the endothelium, regi onal differences in the modulation of nNOS by caveolin isoforms in vascular smooth muscle, and modulation of nNOS by CAV-3 in skeletal muscle.