Calcium binding alteration in plasma membrane from various tissues of spontaneously hypertensive rat

Calcium binding properties of plasma membrane enriched fractions from various tissues were studied in young spontaneously hypertensive rats (SHR) and their normotensive controls (WKY). In all tissues tested (heart, liver, nerve endings, erythrocytes), high affinity calcium binding sites were characterized. Their KD values were in the range of the cytosolic free calcium concentration : (10(-8)-10(-7)). Whatever the tissue, plasma membrane enriched fraction from SHR exhibited a reduced calcium binding capacity but no significant change in affinity. This decrease which averaged 15-25% was also observed in the presence of the calcium ionophore A23187 and thus does not result from a modified accessibility of calcium to its binding sites. It is suggested that this abnormality may be of genetic origin and is possibly implicated in the pathogenesis of hypertension.