Hind-limb/hind-quarter vascular resistance and blood flow changes: possible intrinsic renin-angiotensin system involvement

For many years there was a general belief that the enzyme renin, having bee n secreted into the circulation by the kidney in response to appropriate st imuli, initially generates the inactive decapeptide angiotensin I in the bl oodstream. This is then converted to the biologically active octapeptide an giotensin II by angiotensin converting enzyme on or near, vascular surface receptors both in the lungs and in the organs supplied by the systemic circ ulation. The results of various investigations have, however, latterly led to the conclusion that the overall system is widely distributed throughout the vasculature with the local intracellular formation of angiotensin II. I n this review the reckoned intrinsic renin-angiotensin activity in hind-lim b/hind-quarter is discussed with particular regard to the widespread use of radioimmunoassay, together with a consideration of other factors, more esp ecially ACE inhibition, affecting the relevant regional vascular resistance and blood flow. (C) 2001 Harcourt Publishers Ltd.