Microvascular responses in copper-deficient rats

Abstract

In this study on copper deficiency, the rat crewmaster microcirculation was used as a model for endogenous histamine release and platelet thrombi formation. Male Sprague-Dawley rats were fed either a copper-supplemented diet (CuS, 5 ppm) or a copper-deficient diet (CuD, 0 ppm) for 5 wk before experimentation. The crewmasters of anesthetized rats were spread in a Krebs-filed tissue bath. In venules of CuS animals, photoactivation of intravascular fluorescein isothiocyanate tagged to bovine serum albumin caused significant platelet aggregation and reduction of red blood cell column diameter (RBCCD) by 40 min and stasis of flow by 60 min. In CuD animals there was only minor platelet aggregation and no reduction in RBCCD. Platelet aggregometry studies did not demonstrate reduced platelet aggregation in the CuD group, suggesting that copper deficiency alters the endothelium to inhibit adhesion. Compound 48/80 (1.0 and 10.0 microgram/ml) induced macromolecular leakage in both CuS and CuD groups, with the response in the CuD animals being significantly greater. The results demonstrate that copper deficiency results in alterations of the regulatory mechanisms governing inflammation and thrombosis.

In vitro platelet adhesion to endothelial cells at low shear rates during copper deficiency in rats

“…1 and 2). These results suggest that, although increasing wall shear rate reduces platelet adhesion, shear rate-induced platelet-to-endothelial cell interactions do not contribute to the depressed thrombogenicity seen in copper deficiency [7][8][9]. The results of the current study support reduced platelet adhesion and not altered response to shear force stimuli as the mechanism for our previous in vivo observations of decreased thrombus formation and hemostasis in copper-deficient rats [7][8][9].…”

“…Several investigators have shown that 4 to 5 weeks of dietary copper deprivation has both pro-and anti-aggregatory effects on rat platelet function [7][8][9][25][26][27][28][29]. Our previous in vivo experiments have demonstrated decreased thrombogenesis and prolonged bleeding time in the microcirculation of copper-deficient rats [7][8][9].…”

“…Our previous in vivo experiments have demonstrated decreased thrombogenesis and prolonged bleeding time in the microcirculation of copper-deficient rats [7][8][9]. Recently, we have reported that dietary copper deficiency causes increased ADP-induced platelet aggregation in vitro and decreased platelet adhesion to cultured rat endothelial cells [10] in a static measurement system.…”

“…However, the presence of TEPA on the surface of the endothelial cells after short-term exposure to the chelator did not alter normal platelet adhesion (see Results), indicating that removal of the copper is necessary before adhesion is altered. These data suggest that decreased platelet adhesion due to the effects of copper depletion on both the platelet and the endothelium are responsible for the decreased thrombogenicity seen in dietary copper deficiency [7][8][9].…”

“…We have previously reported an inhibitory effect of dietary copper deficiency on in vivo platelet thrombus formation [7][8][9]. In vitro platelet adhesion to cultured endothelial cells (static conditions) demonstrated that the adherence of platelets from copper-deficient rats to normal endothelial cells was lower [10], while ADP-induced platelet aggregation was greater for copper-deficient platelets than for copperadequate platelets-suggesting that platelet-to-platelet interaction is enhanced [10].…”