EFFECT OF ADRENALECTOMY ON BLOOD PRESSURE IN SALT-FED, HYPERTENSION-PRONE RATS : FAILURE OF HYPERTENSION TO DEVELOP IN ABSENCE OF EVIDENCE OF ADRENAL CORTICAL TISSUE

In adrenalectomized, genetically hypertension-prone rats, a high degree of correlation was found between evidence of functioning adrenal tissue and the development of salt hypertension. There is considerable evidence that some rats have the capacity to regenerate functioning adrenal cortical tissue from accessory glands and microscopic rests, sometimes in remote locations. Therefore, the criteria for continued absence of adrenal function after surgical adrenalectomy are critical. In this study we used three tests to validate the presence, or absence, of adrenal function: (a) a biochemical test, the quantitative, serial measurement of plasma glucocorticoids in individual rats; (b) a physiological test, the ability to survive a virtually sodium-free diet; and (c) the anatomical search for histological evidence of adrenal cortical tissue. Among those animals that developed hypertension after adrenalectomy, the correlation between plasma steroid concentration and blood pressure was statistically significant. We suspect that this correlation exists only during the period when cortical tissue is regenerating; it does not exist among intact animals with and without hypertension induced by salt. It was concluded that some adrenocortical function is necessary for salt hypertension to develop. The evidence was insufficient to settle the question whether the action of corticosteroids is causative, or whether they play a supporting, although necessary, role for an extraadrenal hypertensinogenic factor to become manifest.