Antihypertensive effect of an immunosuppressive agent, cyclophosphamide, in genetically hypertensive rats of the Lyon strain

Abstract

The effect of a pharmacological immunosuppression on the development of hypertension and the part played by hormonal secretions of the thymus in this disease were investigated in genetically hypertensive rats (LH) of the Lyon strain. For this purpose, systolic blood pressure (SBP) was measured in cyclophosphamide-treated LH rats and in neonatally thymectomized LH rats receiving thymostimulin, a thymus extract. Cyclophosphamide treatment delayed the onset and attenuated the full development of hypertension in LH rats whereas it had no effect on SBP in normotensive rats (LN). Thymectomized LH rats also exhibited a significantly decreased SBP as compared to sham-operated controls. Thymostimulin treatment slightly increased the SBP of thymectomized LH rats but did not restore it to the level seen in sham-operated animals. These results showed that thymic hormonal secretions did not seem to be involved in the initiation of hypertension. By contrast, the fact that a reduction of hypertension could be obtained either by thymectomy or cyclophosphamide treatment suggested that immune disorders, mediated by thymus-dependent cellular reactions, could be of pathogenic importance in the development of hypertension in LH rats.