The precise role of nitric oxide (NO) in hypertension is still not fully understood, although this vasodilator system represents the main counterbalance of major pressor systems. The aim of our study was to determine the contributions of superoxide anions, the renin-angiotensin system (RAS), the sympathetic nervous system (SNS) and NO to the maintenance of blood pressure (BP) in Prague hereditary hypertriglyceridaemic (HTG) rats with genetic hypertension. Conscious chronically cannulated rats were subjected to the consecutive blockade of the RAS (losartan, 10mg/kg), the SNS (pentolinium, 5mg/kg) and NO synthase [Nω-nitro-l-arginine (l-NAME), 30mg/kg]. Some additional rats were pretreated with tempol (a membrane-permeable mimetic of superoxide dismutase). A subsequent genetic study in HTG×Lewis F2 hybrid rats (n = 284) was designed to reveal potential associations of particular BP components with baseline BP. The progenitor study indicated that BP elevation was more pronounced in male than female HTG rats (as compared with normotensive Lewis controls). Higher BP in HTG rats was due to the increased residual BP (measured after combined RAS and SNS blockade) and the augmentation of BP responses to tempol or losartan. In contrast, BP responses to pentolinium or l-NAME were similar in all experimental groups. It should, however, be noted that the baseline BP of progenitor animals was correlated positively with both residual BP and the magnitude of the BP response to pentolinium, but not with BP response to l-NAME. Similarly, the baseline BP of F2 hybrid rats was positively associated with residual BP, the BP response to pentolinium and the relative SNS contribution to BP maintenance [expressed as a percentage of baseline mean arterial pressure (MAP) values], as well as with the ratio of BP changes elicited by ganglion blockade and NO synthase inhibition (ΔMAPpentolinium/ΔMAPl-NAME ratio), reflecting the balance of main vasopressor and vasodepressor systems. Thus our studies, performed in progenitor and F2 hybrid rats, revealed that changes in BP induced by l-NAME do not keep pace with the progressive augmentation of pentolinium-induced changes in BP occurring over a wide range of increasing BP. The altered balance between enhanced SNS-dependent vasoconstriction and unchanged NO-dependent vasodilation (‘relative NO deficiency’ in rats with high BP) might result in BP elevation in this form of genetic hypertension.
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Research Article|
February 11 2002
Altered balance of main vasopressor and vasodepressor systems in rats with genetic hypertension and hypertriglyceridaemia
Jaroslav KUNEŠ;
Jaroslav KUNEŠ
1Institute of Physiology, Academy of Sciences of the Czech Republic, and Center for Experimental Research of Cardiovascular Diseases, CZ-142 20 Prague, Czech Republic
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Zdenka DOBEŠOVÁ;
Zdenka DOBEŠOVÁ
1Institute of Physiology, Academy of Sciences of the Czech Republic, and Center for Experimental Research of Cardiovascular Diseases, CZ-142 20 Prague, Czech Republic
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Josef ZICHA
1Institute of Physiology, Academy of Sciences of the Czech Republic, and Center for Experimental Research of Cardiovascular Diseases, CZ-142 20 Prague, Czech Republic
Correspondence: Dr J. Zicha (e-mail Zicha@biomed.cas.cz).
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Publisher: Portland Press Ltd
Received:
July 06 2001
Revision Received:
September 03 2001
Accepted:
October 19 2001
Online ISSN: 1470-8736
Print ISSN: 0143-5221
The Biochemical Society and the Medical Research Society © 2002
2002
Clin Sci (Lond) (2002) 102 (3): 269–277.
Article history
Received:
July 06 2001
Revision Received:
September 03 2001
Accepted:
October 19 2001
Citation
Jaroslav KUNEŠ, Zdenka DOBEŠOVÁ, Josef ZICHA; Altered balance of main vasopressor and vasodepressor systems in rats with genetic hypertension and hypertriglyceridaemia. Clin Sci (Lond) 1 March 2002; 102 (3): 269–277. doi: https://doi.org/10.1042/cs1020269
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