[Relation between the number of vesicles in the vascular smooth muscle cells and extracellular calcium concentration]

The relationship between the number of vesicles in smooth muscle cells in mesenterial arteries and calcium concentration in incubation medium was studied in experiments on normotensive control rats (NKWR) and spontaneously hypertensive rats (SHR). Extracellular elevation of calcium resulted in an increase in the number of vesicles, which was more demonstrable in SHR than in NKWR. After preliminary adrenalectomy the same high concentration of calcium in incubation medium did not induce any changes in the number of vesicles in both animal groups. The decrease of calcium concentration did not produce any changes in the number of vesicles in SHR or NKWR before and after adrenalectomy. The increase of the number of vesicles in response to high extracellular concentration of calcium is assumed to be a means of raising the active surface of the smooth cells and compensates for membrane deficiency seen under pathology.