[Historical Archives of Italian Nephrology. Goldblatt, kidney and hypertension: three steps in the history of nephrology].

The existence of a clear relationship between renal ischemia and hypertension has been widely documented by Harry Goldblatt and his colleagues. In their original papers they showed that gross and persistent elevation of systolic blood pressure could be produced in dogs by clamping both renal artery, or one if the other kidney had been removed. If renal arteries constriction was not too severe, a stable hypertension unaccompanied by more than mild renal impairment was produced. Subsequently, Goldblatt showed that, with severe constriction, retinal changes, arteriolar impairment and left ventricular hypertension could occur. Goldblatt has remained steadily of the opinion that essential hypertension in man is similarly due to renal ischemia occasioned either by stenosis of a main artery, or by organic changes in the smaller renal arteries down to the size of the different glomerular arteries. At first sight, it might seem like a simple matter to correctly identify the chain of events that begins with renal artery constriction and ends with persistent hypertension. Observing that a link was missing in this chain of events, Goldblatt hypothesised that the link was a humoral mechanism. Tigersted and Bergman showed that renin was the missing link. Renal ischemia as cause of hypertension in dogs opened a new chapter in the connection between kidney circulation and blood pressure elevation. This quite unexpected connection is one of the most challenging issues today and clearly demonstrates that the development of Goldblatt's ideas on renal circulation is still important and has by no means ended. Goldblatt, in his epistemologic approach to hypertension scientific challenges, realised that ideas are the building blocks of science: not flights of fancy, not notions sculpted in snow, but enduring concepts. Goldblatt's lasting ideas are more than a function of time and place: they have inherent qualities that have survived up to the present day.