We demonstrated the localization of adenylate cyclase (ACLase) and guanylate cyclase (GCLase) activities in rat aortic endothelium and smooth muscle cells using a recently improved cytochemical method introduced by Fujimoto
et al. (16). Cytochemical effects of some agents (isoproterenol, propranolol, acetylcholine, methylene blue) on cyclase activity were also examined with the direct incubation method
in vivo employing the perfusate added with such agents utilizing the unique location of the aorta.
On the endothelial cell, reaction products indicating ACLase and GCLase activities were localized on the cytoplasmic side of: a) the membrane covering the caveolae and vesicles of both luminal and abluminal surfaces, b) the abluminal plasma membrane underneath the mass of stress fiber-like structure, and c) the gap junctional membrane; and localized around the centriole. On the other hand, the basal activity of GCLase in the smooth muscle cell was intense in comparison with that of ACLase, and the reaction products of both cyclases' activities were localized on the cytoplasmic side of the membrane covering the caveolae, the gap junction, the sarcoplasmic reticulum and the rough endoplasmic reticulum, and on the dense bands, the myosin-like filaments and the centriole. ACLase activity in the endothelial cell and smooth muscle cell was activated by isoproterenol and partly inhibited by propranolol. GCLase activity was stimulated by acetylcholine and fairly reduced by methylene blue in both cell types.
Here, we discuss the assessment of our method and the implications of cytochemical localization of cyclase activity in relation to the functional aspects in endothelium and smooth muscle cells.
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