Microvascular display of xanthine oxidase and NADPH oxidase in the spontaneously hypertensive rat.
OBJECTIVE
Oxygen free radical production in hypertension may be associated with elevated arteriolar tone and organ injury. Previous results suggest an enhanced level of oxygen free radical formation in microvascular endothelium and in circulating neutrophils associated with xanthine oxidase activity in the spontaneously hypertensive rats (SHR) compared with their normotensive controls, the Wistar Kyoto rats (WKY). The aim of this study was to gain more detailed understanding of where oxidative enzymes are located in the microcirculation.


METHODS
An approach was developed to delineate the cellular distribution of two selected oxidative enzymes, xanthine oxidase and nicotinamide adenine dinucleotide phosphate (NADPH) dependent oxidase (protein 67-kDa fraction). Immunolabeling with peroxidase substrate was utilized, which permits full delineation of the primary antibody in all microvascular structures of the mesentery.


RESULTS
Xanthine oxidase is present in the endothelium of all segments of the microcirculation, in mast cells, and in parenchymal cells of the mesentery. NADPH oxidase can be detected in the endothelium, leukocytes, and mast cells and with lower levels in parenchymal cells. The mesentery of WKY and SHR has similar enzyme distributions with enhancements on the arteriolar and venular side of the microcirculation that coincide with the sites of enhanced free radical production recently reported. Immune label measurements under standardized conditions indicate that both enzymes are significantly enhanced in the SHR. Adrenalectomy, which serves to reduce the blood pressure and free radical production of the SHR to normotensive levels, leads to a reduction of NADPH and xanthine oxidase to normotensive levels, while supplementation of adrenalectomized SHR with dexamethasone significantly increases the oxidase expression in several parts of the microcirculation to levels above the WKY rats.


CONCLUSIONS
The results indicate that enhanced expression of NADPH and xanthine oxidase in the SHR depends on an adrenal pathway that is detectable in the arteriolar and venular network at high and low pressure regions of the circulation.
DeLano
Frank A
FA
Department of Bioengineering and The Whitaker Institute for Biomedical Engineering, University of California, San Diego, La Jolla, 92093-0412, USA.
Parks
Dale A
DA
Ruedi
Julie M
JM
Babior
Bernard M
BM
Schmid-Schönbein
Geert W
GW
D000311:Adrenal Glands / Q000502:physiology; D000315:Adrenalectomy; D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D006973:Hypertension / Q000201:enzymology*; D007962:Leukocytes / Q000201:enzymology; D008297:Male; D008643:Mesentery / Q000098:blood supply / Q000201:enzymology; D008833:Microcirculation / Q000187:drug effects / Q000201:enzymology*; D019255:NADPH Oxidases / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014018:Tissue Distribution; D014969:Xanthine Oxidase / Q000378:metabolism*
D005609:Free Radicals; D003907:Dexamethasone; D014969:Xanthine Oxidase; D019255:NADPH Oxidases