The renin-angiotensin-system in the skin. Evidence for its presence and possible functional implications

Among the several hormonal systems regulating body functions, the renin-angiotensin-system has long been considered a classical endocrine system with angiotensin II, its effector hormone, being synthesized in and subsequently distributed by the circulation to act on its numerous, mainly renal and cardiovascular target organs throughout the body. Angiotensin II has long been regarded to be primarily responsible for the regulation of blood-pressure and of volume- and electrolyte-homeostasis. Recent evidence suggests that it also affects cellular proliferation and differentiation via the so-called local or tissue-renin-angiotensin-systems. Such trophic actions have already been observed in tissues not belonging to the renal or cardiovascular systems such as cultured cells of neuronal origin. Evidence for a rôle of angiotensin II in the skin is so far scanty and mainly based on the demonstration of angiotensin receptors on cultured human keratinocytes and in subcutaneous tissue of rats. Although almost every single component of the renin-angiotensin-system has already been identified in skin of one or another species, comprehensive data regarding the skin renin-angiotensin-system as a whole within one particular species, especially in man, are still lacking. The present manuscript reviews novel recent data regarding the renin-angiotensin-system particularly in skin, and it discusses a possible functional rôle of the cutaneous renin-angiotensin-system on the basis of these findings.