Expression of cardiac renin and its modulation by stress in normotensive and hypertensive rats.

Renin is the rate-limiting step in angiotensin II production. Existence of the cardiac renin is still ambiguous in healthy animals, although there is evidence that under some pathological conditions the heart might express mRNA for renin. Therefore, the aim of the present study was to (i) detect the renin gene expression in the whole rat heart, ventricles, atria and in isolated and purified myocytes, (ii) determine the effect of stress on renin mRNA and protein levels, and (iii) compare the response of renin gene expression to stress in normotensive and spontaneously hypertensive rats. Renin mRNA was determined by reverse transcription and polymerase chain reaction and quantified relatively to beta-actin and glyceraldehyde-3-phosphate dehydrogenase. Protein message was detected by monoclonal antibody against renin. Renin mRNA was found in all parts of the heart and in myocytes. Renin protein was found in the heart ventricles and atria, but not in cardiomyocytes. Immobilization stress affected renin on both, the mRNA and the protein level. The effect of stress was observed in the hearts of normotensive, but not in genetically hypertensive rats. Thus, renin might be involved in the development of the pathophysiological state in rat heart.