In DOCS one-renin gene normotensive mice with severe hypokalemia (serum K: 2.76 ± 0.14), we have observed cardiac and vascular hypertrophy, left ventricular dysfunction, and coronary perivascular fibrosis with upregulation of cardiac Col-I and III fibrotic genes as well as overproduction of their proteins. This evidence concerns the gene REN and vascular smooth muscle hypertrophy.