Calcium transport and protein content in cell plasma membranes of spontaneously hypertensive rats

In the absence of depolarizing agents, 45Ca uptake by synaptosomes of the brain tissue of spontaneously hypertensive rats (SHR) was 40% greater than in normotensive controls. This difference disappeared after membrane treatment with depolarizing agents or with the addition of the Ca channel blocker verapamil. Increased 45Ca uptake was also observed in isolated platelets of SHR. It can be assumed that in both cases these differences were caused by partial depolarization of the plasma membrane as a result of its increased permeability to Na+. The addition of calmodulin to microsomal fractions of SHR brain tissue resulted in a considerably diminished increase in ATP-dependent calcium accumulation. These data are in accord with previous findings obtained in a study on the erythrocyte membrane Ca pump. Data obtained by means of differential scanning microcalorimetry of erythrocyte membranes and gel electrophoresis of membrane proteins indicated a higher band-3 protein content in the erythrocyte membranes of SHR. These data support the concept of primary hypertension as a type of generalized membrane pathology.