Cardiac contractile and coronary flow reserves in deoxycorticosterone acetate-salt hypertensive rats.

Abstract

SUMMARY Cardiac contractility and coronary flow were compared in conscious rats with established deoxycorticosterone acetate-salt hypertension and in those with sham treatment. The hypertensive rats showed a 32% increase in left ventricular/body weight ratio at 9 weeks of treatment and 42% at 18 weeks of treatment. Resting peak rate of change of pressure (dp/dt) was unchanged at 9 weeks and increased at 18 weeks in hypertensive rats, while isoproterenol-stimulated maximal, propranololinduced minimal, and Ca 2+-stimulated maximal peak dp/dt were greater at 18 weeks. These data indicate the preservation of contractile function. At 18 weeks, the /3-adrenergic receptor-mediated contractile reserve, estimated from isoproterenol-stimulated maximal and resting peak dp/dt, was reduced but the propranolol-induced decrease in peak dp/dt was increased in hypertensive rats compared with sham-treated rats. Thus, at this stage, a greater portion of the total contractile capacity appeared to be mobilized with prolongation of hypertension and progression of left ventricular hypertrophy. No differences were observed in left ventricular and right ventricular coronary flow (microspheres) and left ventricular inner/outer flow ratio at rest and with dipyridamole-induced maximal coronary dilatation, at 9 and 18 weeks. There were no alterations in left or right ventricular coronary flow reserves, as estimated from resting and dipyridamole-induced values. The minimal coronary vascular resistance (normalized for gram of tissue) of both the left and right ventricles was increased at either stage, which suggests the occurrence of structural coronary vascular changes. Thus, basal coronary flow and a coronary flow reserve were uncompromised despite evidence of structural coronary vascular alterations in these hypertensive rats. (Hypertension 7: 569-577, 1985) KEY WORDS • left ventricular hypertrophy • minimal coronary vascular resistance peak rate of change of pressure (dp/dt) • radioactive microspheres • isoproterenol propranolol • dipyridamole S YSTEMIC hypertension often leads to alterations in cardiac performance associated with an increase in cardiac mass 1 "" and coronary circulation. '-l2 " 19 There is still considerable controversy regarding cardiac performance in the presence of hypertension, 1 ""-l3 most of which stems from the wide spectrum of cardiac function caused by variations in the duration, severity, and type of hypertension.Little is known of cardiac function and coronary hemodynamics in deoxycorticosterone acetate (DOCA)-salt hypertension. The literature seems to consist of reports on the unaltered mechanical properties of isolated papillary muscles 13 and the increased intercapillary distance of superficial epicardial muscles. 19 In view of this and earlier data on some features of hemodynamic, 20 neurohumoral, 2 '-" and myocardial and coronary vascular histopathological 12 changes in this form of hypertension, we wanted to assess cardiac function and coronary hemodynamics in DOCA-salt hypertensive rats. Since we ...

β-Adrenergic Reactivity in Conscious DOCA-Salt Hypertensive Rats

“…However, a similar fall in MAP has been reported in DS intact and DS sham rats after isoprénaline infusion at doses ranging from 40 to 160 ng/kg/min for 5-min periods [39]. Our results show that the infusion of differ ent doses of isoprénaline produced a greater drop in MAP in the different groups of DS rats than in US groups.…”

Effects of moderate diabetes on cardiac performance in spontaneously hypertensive and Wistar-Kyoto rats.

“…Peak LV pressure and peak LV dP/dt,^ are influenced mainly by contractility and cardiac mass. 16 " 19 The differences in these parameters seen between diabetic and control SHR and between control SHR and WKY at 20 weeks may be ascribed in part to differences in cardiac mass (LV weight) and, hence, in cardiac contractile units.…”

“…This part of the experiments was completed within 20 minutes of calibration, since a considerable time-dependent baseline drift occurred with this catheter, thereby making the pressure reading unreliable with time. 19 The microtip catheter was then withdrawn, and the aortic occluder was detached.…”

Cardiovascular responses to acute stress in young-to-old spontaneously hypertensive rats.

“…Tip-tapered PE-50 catheters (Clay Adams, Parsippany, NJ, USA) were introduced into the femoral artery and vein, respectively, and into the left ventricle through the right carotid artery. 22 - 30 All catheters were brought out through subcutaneous tunnels in the dorsal cervical region. The wounds were treated with 1% lidocaine and sutured.…”

“…Cardiac and peripheral hemodynamic variables were calculated using the reference and tissue sample radioactivity, based on standard equations. 22 - 30 Cardiac output and regional blood flow were reported as ml/min/100 g of body or tissue weight; cardiac output was referred to as cardiac index. Total peripheral and regional vascular resistances were expressed as mm Hg/ml/min/100 g of body or tissue weight.…”