EDN1 and retinitis pigmentosa 1: Moreover, increased endothelin-1 (ET-1) plasma levels have been described repeatedly in RP [5–7], and this increase might play a key role in determining vasoconstriction and ischemia, reducing ocular blood flow [8, 9], and leading to worsening of the abiotrophic process, as previously reported by our group in early stage RP [10].