Erythrocyte deficiency in calpain inhibitor activity in essential hypertension.

The calpain-calpain inhibitor system was evaluated in erythrocytes of patients with essential hypertension and normotensive controls, either with or without a family history of hypertension. Calpain levels were similar in the controls and hypertensive patients, whereas the inhibitor activity level was significantly reduced in the latter (301.8 +/- 26.4 vs 220 +/- 14 U/mg hemoglobin, p less than 0.001). Borderline hypertensive patients and a few controls with a history of hypertension showed low inhibitor activity. Similar results have recently been reported in genetically hypertensive rats of the Milan strain. A significant inverse correlation (r = -0.43, p less than 0.001) was found between mean arterial pressure and calpain inhibitor. Although the pathophysiological significance of these observations is not yet clear, they suggest a new area of investigation into the molecular mechanisms underlying essential hypertension and its complications.