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The morphological effect of endothelin-1 (ET-1) and the distribution of endothelin-binding sites on the kidney and lung was investigated ultrastructually by intravenous injection of [I]-ET-1 into rats. About 10% decrease of the diameter of glomeruli was observed at 10 min after the injections of ET-1 or [I]-ET-1 (1.3-2.4 nmole/kg). When localization of [I]-ET-1 in the kidney was examined by light and electron microscopic radioautography, silver grains were preferably localized on the fenestrated endothelial cells of glomeruli and peritubular capillary endothelial cells. Some grains were also localized on the interdigitating processes of urinary tubules. Quantitative analysis of silver grains in the glomeruli showed that 83% of grains were located on the fenestrated endothelial cells, 12% on the podocytes of visceral cells, and 5% on mesangial cells at 10 min. After 60 min, 50% of silver grains were incorporated into the cytoplasm of fenestrated endothelial cells. In contrast to glomeruli, silver grains were rare on the arteries and large arterioles. However, a few silver grains were often observed on the smooth muscle cells of small arterioles (8-20 μm in diameter). In the lung, 70% of silver grains were located on the alveolar capillary endothelial cells. These results indicate the abundance of ET receptors on the glomerular fenestrated endothelium, peritubular fenestrated endothelium and alveolar capillary endothelium. [ABSTRACT FROM AUTHOR]

Localization of intravenously injected [I]-endothelin-1 was examined in rat liver by light and electron microscopic radioautography. At 10 min after injection, silver grains were localized along the sinusoidal wall, i.e., mostly on the thin processes of fat-storing cells and sinusoidal endothelial cells, and also on the Kupffer cells and the microvilli of hepatocytes. About 35% of the total silver grains were located on the processes of fat-storing cells at 10 min. The grain density (number of silver grains/cell area) of fat-storing cells was three-fold that of Kupffer cells, and 18-fold that of hepatocytes. At 60 min, 60% of the total grains were observed on the fat-storing cells, though the value of grain density was not changed. Silver grains were internalized into the cytoplasm of fat-storing cells and often associated with multivesicular bodies. In contrast, the grain density of endothelial cells and Kupffer cells decreased with time. These results indicate that hepatic fat-storing cells have a considerable number of endothelin-binding sites, and incorporate bound endothelin into cytoplasm. [ABSTRACT FROM AUTHOR]