President Reagan has signed a proclamation designating the final week of April as National Organ and Tissue Donor Awareness Week.

Reagan, in signing the document released Friday, urged health care professionals, public and private service organizations and all Americans to support "this humanitarian cause" of organ and tissue donation."Thousands of Americans will receive an extraordinary gift this year a kidney, heart, liver, pancreas, a combination of heart and lung, skin, a cornea, bone, or bone marrow," said the proclamation. "The great majority of these gifts will have been possible only because a caring American agreed to donate an organ or tissue for transplantation."

But Reagan conceded such action must be accompanied by "thorough reflection and complete information." "Recent medical and technological developments are posing new moral and ethical questions about transplantation," the document said.