Cellular NO Synthase in Various Murine Tissues and Organs

Cellular NO synthase was assayed in bone marrow, spleen, thymus, lymph nodes, epidermis, hypodermic connective tissue, small gut, peritoneal exudate, liver, kidney, and heart by cytochemical and immunofluorescent methods. As a rule the enzymatic activity was found in differentiated cells that finished proliferation (mature hemopoietic cells, epithelium of gut villi, etc.). The enzyme activity was undetectable in actively reproducing low-differentiated cells (basal layer of the epidermis, crypt cells of the small gut, or blast hemopoietic forms). NO is proposed to participate in regulation of tissue-specific terminal differentiation (maturation) of the cells.