[Morphology and stereology of the myocardium in hypertensive rats. Correlation with the time of nitric oxide synthesis inhibition].
OBJECTIVE
To study structural changes of the myocardium in relation to the time of nitric oxide synthesis inhibition.


METHODS
Four groups of 10 rats each were studied: 2 control groups and 2 groups with administration of L-Name (50 mg/kg/day), one during 25 days and the other during 40 days. The animals were then sacrificed and the hearts were prepared for study in light microscopy, where sections strained by picro-sirius were studied with and without polarized light for analysis of the cardiac interstitium collagen. Volume densities of myocytes (Vv[m]) and interstitium (Vv[int]), the numerical density of myocytes (Nv[m]) and the mean cross-sectional area of myocytes were (A[m]) also determined.


RESULTS
The L-Name animals were compared with the respective controls. In the L-Name rats, the tail arterial pressure increased 74.5 and 90.2% in the 25 days group and in the 40 days group, respectively. The heart weight increased 50% in the 25 days group and 28.6% in the 40 days group. The myocardium of the L-Name animals presented myocyte hypertrophy with increased A(m), perivascular and interstitial fibrosis, thickness of the tunica intima and tunica media of the intramyocardial arteries. In the 40 days group the L-Name animals had decreased Vv(m) and Nv(m) and increased Vv(int).


CONCLUSIONS
Inhibition of nitric oxide synthesis provokes myocardial changes that progress with the time of L-Name administration. The stereology is useful to determine and to evaluate the myocardial changes in this model of arterial hypertension.
Instituto de Biologia Roberto Alcântara Gomes, Laboratório de Morfometria e Morfologia Cardiovascular, UERJ.
L M
LM
Pereira
G M
GM
Vianna
C A
CA
Mandarim-de-Lacerda
D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006973:Hypertension / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000201:enzymology / Q000473:pathology*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D009929:Organ Size; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D004791:Enzyme Inhibitors; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester