Possible link between converting enzyme inhibition and renomedullary interstitial cells

The kidney exerts both prohypertensive and antihypertensive functions. Part of the anti-hypertensive function of the kidney is mediated by the renomedullary interstitial cells (RIC), as an endocrine-type function. Six experimental models of hypertension and their relation to the antihypertensive function of the RIC are discussed. It is proposed that the anti-hypertensive function of the RIC may be deficient by the three mechanisms: 1) absence of the cells (as in the renoprival state); 2) severe damage to the cells (as in partial nephrectomy-salt hypertension of the rat and late malignant hypertension of the rabbit); and 3) constraint of the function of these cells (as in angiotensin-salt hypertension due to a lower salt intake). The constraint may result from excessive angiotensin, either by a direct effect or via a hemodynamic mechanism. The converting enzyme inhibitors (CEI) fail to exert their antihypertensive function when the RIC are absent or damaged. Conversely, the CEI are effective in those models associated with intact RIC. CEI appear to exert their antihypertensive action partly through an effect on RIC.