Ta. Uggere et al., The cardiopulmonary reflexes of spontaneously hypertensive rats are normalized after regression of left ventricular hypertrophy and hypertension, BRAZ J MED, 33(5), 2000, pp. 589-594
Citations number
15
Categorie Soggetti
Medical Research General Topics
Journal title
BRAZILIAN JOURNAL OF MEDICAL AND BIOLOGICAL RESEARCH
Cardiopulmonary reflexes are activated via changes in cardiac filling press
ure (volume-sensitive reflex) and chemical stimulation (chemosensitive refl
ex). The sensitivity of the cardiopulmonary reflexes to these stimuli is im
paired in the spontaneously hypertensive rat (SHR) and other models of hype
rtension and is thought to be associated with cardiac hypertrophy. The pres
ent study investigated whether the sensitivity of the cardiopulmonary refle
xes in SHR is restored when cardiac hypertrophy and hypertension are reduce
d by enalapril treatment. Untreated SHR and WKY rats were fed a normal diet
. Another groups of rats were treated with enalapril (10 mg kg(-1) day(-1),
mixed in the diet; SHRE or WKYE) for one month. After treatment, the volum
e-sensitive reflex was evaluated in each group by determining the decrease
in magnitude of the efferent renal sympathetic nerve activity (RSNA) produc
ed by acute isotonic saline volume expansion. Chemoreflex sensitivity was e
valuated by examining the bradycardia response elicited by phenyldiguanide
administration. Cardiac hypertrophy was determined from the left ventricula
r/body weight (LV/ BW) ratio. Volume expansion produced an attenuated renal
sympathoinhibitory response in SHR as compared to WKY rats. As compared to
the levels observed in normotensive WKY rats, however, enalapriI treatment
restored the volume expansion-induced decrease in RSNA in SHRE. SHR with e
stablished hypertension had a higher LV/BW ratio (45%) as compared to normo
tensive WKY rats. With enalapril treatment, the LV/BW ratio was reduced to
19% in SHRE. Finally, the reflex-induced bradycardia response produced by p
henyldiguanide was significantly attenuated in SHR compared to WKY rats, Un
like the effects on the volume reflex, the sensitivity of the cardiac chemo
sensitive reflex to phenyldiguanide was not restored by enalapril treatment
in SHRE. Taken together, these results indicate that the impairment of the
volume-sensitive, but not the chemosensitive, reflex can be restored by tr
eatment of SHR with enalapril. It is possible that by augmenting the gain o
f the volume-sensitive reflex control of RSNA, enalapril contributed to the
reversal of cardiac hypertrophy and normalization of arterial blood pressu
re in SHR.