Lanthanum staining of coronary microvascular endothelium: Effects of ischemia reperfusion, propranolol, and atenolol

Abstract

Cat isolated hearts were perfused via the aorta with normothermic arterial blood from donor cats. After 1 hr of equilibration, dl-propranolol (1.9 mg/kg), atenolol (1.65 mg/kg), or physiological saline solution was infused via the aortic cannula. The hearts were made globally ischemic for 1 hr and reperfused for 1 hr. Hearts given saline but not made ischemic, and hearts from blood-donor cats served as controls. The hearts were flushed with physiological saline for 2 min, then perfused with cacodylate-buffered glutaraldehyde containing 1% LaQ. Samples of left ventricle were postfixed in osmium and prepared for electron microscopy. Microvessels in nonischemic tissues had heavy La3+ staining on luminal surfaces of endothelial cells. Many plasmalemmal vesicles along luminal surfaces of endothelial cells were filled with Las+. Several vesicles appeared to open onto both surfaces thus forming channels through the endothelium. Lanthanum penetrated into, and occasionally through, interendothelial junctions. Endothelial cells lining vessels in ischemic myocardium were swollen, had pale cytoplasm, and showed little La3+ on the luminal surfaces. Few plasmalemmal vesicles were present and the mitochondria contained deposits of Las+. Extravascular spaces were distended but interendothelial junctions seemed to be intact. Lanthanum staining and morphology of endothelial cells in hearts treated with propranolol or atenolol were very similar to nonischemic myocardium. The data suggest that the B-blocking agents, propranolol and atenolol, maintain the integrity of coronary vascular endothelium during ischemia.

Rapid modification of the glycocalyx caused by ischemia-reperfusion is inhibited by adenosine A2Areceptor activation

“…It is clear that one of the primary manifestations of reperfusion injury is microvascular dysfunction, which is centered largely on the endothelial cell (8,12). Microvascular dysfunction includes increased permeability, cell swelling, increased expression of endothelial adhesion molecules, increased leukocyte adhesion (1,8,12), and disruption of the glycocalyx (5,17,28). While the molecular causes of the dysfunction are not clear, previous work in this laboratory has shown that the glycocalyx is a dynamic structure that can respond rapidly to a number of stimuli, including production of reactive oxygen species (49) and TNF-␣ (30).…”

“…Several studies using electron microscopy have shown that I/R injury causes significant damage to the endothelial glycocalyx (5,17,28). One of these studies found that the glycocalyx was entirely removed from the endothelium after 1 h of ischemia and 1 h of reperfusion (28) of feline coronary capillaries.…”

“…A number of previous reports have concluded that I/R can disrupt normal glycocalyx function/structure (5,19,28). However, a major limitation of these studies has been the use of electron microscopy in experimental measurements.…”

“…The glycocalyx also responds to various inflammatory stimuli, including oxidized low-density lipoproteins (13,48) and TNF-␣ (30). Moreover, electron microscopy has shown that thickness and uniformity are reduced after ischemia-reperfusion (I/R) (5,18,28).…”

17β-Estradiol as a Receptor-Mediated Cardioprotective Agent

“…Upon completion of the designated protocol, hearts were perfused for 3 min with 2.5% glutaraldehyde and 1% LaCl 3 in 0.1 M sodium cacodylate buffer (pH 7.44). The electron-dense LaCl 3 serves as an indicator of blood vessel integrity (Haack et al, 1981). Tissue samples from the left ventricular myocardium immediately below the site of occlusion were cut into segments measuring approximately 1 mm on a side.…”