Differential biomechanics in resistance arteries of male compared with female Dahl hypertensive rats

This study assessed vasodilator responses in skeletal muscle resistance arteries (100-250 microns) from rats with chronic (4-8 wk) reduced renal mass (RRM) hypertension and normotensive sham-operated controls on a high (4% NaCl; HSSHAM)- or low (0.4% NaCl; LSSHAM)-salt diet. Arteries from RRM hypertensive rats [normal and high-salt diet (HSRRM)] and a separate group of spontaneously hypertensive rats exhibited an impaired dilation in response to reduced PO2 compared with those of their normotensive controls. Prostacyclin release, assessed by radio-immunoassay for 6-ketoprostaglandin F1 alpha, increased significantly in response to reduced PO2, but was unaffected by hypertension or salt intake. Dilator responses to acetylcholine and the prostacyclin analog iloprost were significantly reduced in both HSRRM and HSSHAM compared with LSSHAM rats. Dilation in response to direct activation of adenylate cyclase with forskolin or guanylate cyclase with the nitric oxide donor sodium nitroprusside was not significantly different in HSRRM, HSSHAM, and LSSHAM rats. These results indicate that hypoxic dilation is impaired in skeletal muscle resistance arteries of hypertensive rats and that chronic high-salt diet alone leads to impaired vasodilator responses in resistance arteries of normotensive animals, possibly via abnormalities in membrane function or G protein signaling rather than impaired second-messenger function.

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Contractile responses and signal transduction of endothelin-1 in aorta and mesenteric vasculature of adult spontaneously hypertensive rats

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y93-069 ◽

1993 ◽

Vol 71 (7) ◽

pp. 473-483 ◽

Cited By ~ 19

Author(s):

Paul V. Nguyen ◽

Xiao-Ping Yang ◽

Guo Li ◽

Li Yuan Deng ◽

Jean-Pierre Flückiger ◽

...

Keyword(s):

Inositol Phosphates ◽

Second Messengers ◽

Resistance Arteries ◽

Hypertensive Rats ◽

Contractile Responses ◽

Spontaneously Hypertensive ◽

Wky Rats ◽

Mesenteric Arterial Bed ◽

Mesenteric Vessels ◽

Wistar Kyoto

The contractile responses and generation of intracellular second messengers in response to endothelin-1 (ET-1), a potent vasoconstrictor peptide released locally by endothelial cells and involved in the regulation of vascular tone, were investigated in different segments of the vascular tree of adult 18-week-old spontaneously hypertensive rats (SHR) as compared with age-matched Wistar–Kyoto (WKY) rats. Aorta rings of SHR showed lower maximum response to ET-1 in comparison with WKY rats. Rings of the main superior mesenteric artery of SHR and WKY showed similar responses to ET-1. Small mesenteric resistance arteries of SHR, mounted on a wire myograph, developed similar tension to those of WKY rats in response to ET-1. The dose–response of inositol phosphates to ET-1 was significantly blunted in thoracic aorta of SHR compared with WKY rats, whereas it was similar in the mesenteric arterial bed. Baseline 1,2-diacylglycerol content was higher in thoracic aorta of SHR than WKY, while it was similar in the mesenteric arterial bed of the two strains. The response of 1,2-diacylglycerol to ET-1 was blunted in aorta of SHR, whereas no significant differences in diacylglycerol accumulation could be found in mesenteric vessels between SHR and WKY. In small mesenteric arteries, the dose–response to ET-1 of cytosolic free calcium, measured with the fluorescent dye Fura 2-AM, was similar in the two groups of rats. We conclude that in the aorta of 18-week-old SHR there is reduced generation of second messengers (inositol phosphates and diacylglycerol), which underlies its decreased response to ET-1 In mesenteric vessels (both proximal and distal) signal transduction is similar in SHR and WKY, and as a result contractile responses in both species are comparable. The responses to ET-1 of the arterial tree in terms of contractility and second messenger generation may reflect the adaptive processes taking place as a consequence of elevated blood pressure within the arterial wall of different segments of the vasculature of SHR.Key words: inositol phosphate, phospholipids, diacylglycerol, cytosolic calcium, second messengers, conduit and resistance arteries, Wistar–Kyoto rats.

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