Endothelial specific granules in the umbilical veins of the postnatal rabbit

Abstract

A remarkable increase in number of endothelial specific granules was observed in the rabbit umbilical veins between 2 and 5 days after birth. Electron microscopy indicated that the granules were segregated in the Golgi complex of the endothelial cells and released into the vascular lumen during the postnatal obliteration stage of this vessel. Incubation of the postnatal vessels in Ringer solution containing a histamine-releasing compound induced remarkable morphological alterations of these cytoplasmic components; a reduction of their osmiophilia, swelling with a widened space separating the granular matrix from the limiting membrane, fusion to each other and expulsion of their contents into the vascular lumen, as in mast cell degranulation by this drug, were noted. High-performance liquid chromatography of the homogenized vessels demonstrated appreciable concentrations of histamine in the postnatal samples. There was a correlation between the histamine concentration and the quantity of granules in the respective postnatal samples. The present study strongly suggests that the granules are reservoirs of histamine and have an important role in the obliteration of this vessel.

Enhancement of immunoreactivity for endothelin-1 and endothelin-converting enzyme-1 in the cadmium-treated rat thoracic aorta

“…The increase of WP bodies in the aortae after treatment with cadmium has already been reported by Yoshizuka et al [36] and Doi et al [4], and we consider that this increase is mainly due to the enhanced segregation of WP bodies from trans-Golgi networks as indicated by Fujimoto et al [7]. WP bodies are known to be storage sites of certain vasoactive substances such as histamine [3,9,32], ET-1 [4,10,12,22,27], and calcitonin gene-related peptide [5,24].…”

“…WP bodies are known to be storage sites of certain vasoactive substances such as histamine [3,9,32], ET-1 [4,10,12,22,27], and calcitonin gene-related peptide [5,24]. The involvement of WP bodies in the extracellular release of these substances into both vascular lumen and subendothelial layer by degranulation and/or exocytosis in a manner of regulated release has already been reported in the toad aorta [3,6] and in the rabbit umbilical vein [7,27]. Russell et al [26] demonstrated the localization of ECE-1 in WP bodies in the cultured human umbili- cal vein using immunoelectron microscopy and insisted on the crucial roles of WP bodies in a manner suggestive of regulated ET-1 release.…”

Neovascularization in the pre‐ and postnatal rabbit corpora cavernosa penis: Light and electron microscopy and autoradiography

“…Since the first description of endothelial specific granules in the dog artery (Weibel and Palade, 19641, the nature and function of Weibel-Palade bodies have been investigated by many workers. Based on analysis by high-performance liquid chromatography, we have suggested that they may contain some vasoconstricting factors such as histamine (Fujimoto, 1982;Fujimoto et al, 1982). Carstens (1981) proposed the use of Weibel-Palade bodies for the identification of endothelial character.…”

Histamine Disposition in Endothelial Specific Granules of the Toad Aorta

“…Burri and Weihel [1968] suggested that the granules might contain some procoagulative substances since the epinephrine-perfused rabbit aortas released a coagula tion-activating substance into the perfusate. In our pre vious experiments, marked degranulation resulted in the toad aortas after incubation with Ringer's solution con taining compound 48/80, a histamine liberator [Fujimoto, 1982;Fujimoto et al, 1982). Since incubation of these vessels in Ringer's solution only did not affect these granules, the degranulation seemed to be induced by histamine release from the granules.…”