Estudo quantitativo da microcirculaçäo miocárdica na hipertensäo arterial por progressiva inibiçäo da síntese do óxido nítrico / Quantitative study of myocradial microcirculation in arterial hypertension due to progressive inhibition of NO synthesis

ABSTRACT

OBJECTIVE- To study the quantitative changes in intramyocardial blood vessels in rats in whom nitric oxide synthesis was inhibited. METHODS - Four groups of 10 rats were studied control (C25 and C40) and L-NAME(L25 and L40). The animals L25 and L40 received L-NAME in the dosage of 50mg/kg/day for 25 and 40 days, respectively. On days 26 and 41 the animals in groups 25 and 40 were sacrificed. Analysis of the myocardium was performed using light microscopy and stereology. RESULTS - Arterial blood pressure and heart weight increased 74.5 and 57.8 per cent after 25 days and 90.2 and 34.6 per cent after 40 days, respectively. Comparing the L-NAME rats with the respective controls revealed that vessel volume density decreased 31.3 per cent after 40 days, and the vessel length-density decreased 53.5 per cent after 25 days and 25.7 per cent after 40 days. The mean cross-sectional area of the vessels showed an important reduction of 154.6 per cent after 25 days. The intramyocardial vessels decreased significantly in length- density in the L-NAME animals. The mean cross-sectional area of the vessels, which normally increases during heart growth between 25 and 40 days, showed a precocious increase by the 25th day in the L-NAME rats. This suggests an increase of the size of the heart, including blood vessels. CONCLUSION - The inhibition of the NO synthesis provokes rarefaction in the intramyocardial vessels that progresses with the time of administration of L-NAME.