Selective Suppression of an Endothelin and Platelet-Derived Growth Factor Containing Vesicular System in Endothelium of Rat Saphenous Vein by Long-Term Orthostasis

Abstract

Electron-dense vesicles were observed in rat vascular endothelium. The purpose of this study was to characterize their content(s), venous-arterial distribution and response to chronic orthostatic stress in extremity vessels. Saphenous and brachial vessels – saphenous vein (SV), saphenous artery (SA), brachial vein, brachial artery – were prepared for electron microscopy to quantitate the vesicle area within the endothelium following immunohistochemical and immunocytochemical identification. The effect of long-term orthostasis was assessed by exposure to head-up tilt for 2 weeks. The vesicular area in relation to the total cross-sectional area of the endothelial cells in the SV and SA of normal and confined control groups was 3.88 ± 0.38 versus 0.89 ± 0.06% (p < 0.05) and 4.92 ± 0.25 versus 1.09 ± 0.47% (p < 0.05), respectively. Head-up tilt suppressed the vesicle content of the SV to 2.26 ± 0.39% (p < 0.05), but it remained low in the SA (1.29 ± 0.45%), brachial vein (0.45 ± 0.12%) and brachial artery (0.59 ± 0.17%). Endothelin and platelet-derived growth factor, but not acidic phosphatase activity or lipid content, could be identified in the vesicles. Plasma endothelin levels were unchanged. We conclude that dense vesicles in the endothelium of extremity vessels are not cell degradation products. They may represent a vesicular secretory or storage system for endothelin and platelet-derived growth factor which participates in regional vascular adaptation to long-term orthostatic load.

Structural and functional responses of extremity veins to long-term gravitational loading or unloading—lessons from animal systems

“…Food intake and drinking activity of the animals were not inhibited by the long-term orthostatic body position [9]. The head-down posture resulted in a transient depression of feeding activity during the first few days of tilting only [11]. The locomotor behavior of the rats was characterized using a videocomputer-based infrared tracking method that continuously recorded and quantized the movement of these rats throughout day-and-night with a high time resolution [12].…”

Does Chronic Experimental Head-Down Tilt Alter Intramural Innervation Density of Limb Blood Vessels?

“…proximately 0.1-0.2 µm diameter (which we identified in the endothelium cells of rat saphenous vein) greatly decreased during two weeks of orthostatic body position [9,10].…”

“…We assume that the quasi-free locomotor exercise the tilted animals in the long tubular cages were allowed may counteract a possible suppressive effect of chronic head-down tilt on hind-limb vascular innervation density. [The Japanese Journal of Physiology 55: [127][128][129][130][131][132][133][134] 2005] Key words: brachial vein, head-down tilt, saphenous artery, saphenous vein, vascular innervation.proximately 0.1-0.2 µm diameter (which we identified in the endothelium cells of rat saphenous vein) greatly decreased during two weeks of orthostatic body position [9,10].After 2 weeks of 45° head-tilting, among the most interesting observations we made in this model of orthostasis was a surprisingly large increase (nearly double) in the adventitial (intramural) sympathetic innervation density of hind-limb blood vessels, especially the veins [2]. This increase included both the density of nerve terminals (NTD) and the number of synaptic microvesicles in the terminals (SVC).…”

Papel da endotelina no estresse ortostático

“…White et al (1998) Raffai et al (2005) investigaram vesículas eletro-densas no endotélio vascular quanto a sua constituição, distribuição arteriovenosa e a resposta ao estresse ortostático crônico de vasos de extremidade. A endotelina e fator de crescimento derivado de plaqueta foram identificados nas vesículas.…”

“…A endotelina e fator de crescimento derivado de plaqueta foram identificados nas vesículas. Raffai et al (2005) concluíram que as vesículas densas no endotélio de vasos de extremidade podem representar um sistema secretório vesicular, ou de armazenamento de endotelina e fator de crescimento derivado de plaquetas que participam na adaptação vascular regional à carga ortostática em longo prazo.…”