Somatomedin: inhibiton of adenylate cyclase activity in subcellular membranes of various tissues.

Somatomedin in concentrations between 3 and 20 units per milliliter significantly inhibits the basal activity of adenylate cyclase in crude membrane preparations obtained from homogenates of fat cells, liver, and spleen lymphocytes of the rat, and from chondrocytes and cartilage of chick embryos. The enzyme activity measured in the presence of stimulating hormones (epinephrine, prostaglandin PGE(1), parathyroid hormone) is also inhibited in these preparations by somatomedin. These observations may be relevant in a general way to the mechanism of action of growth-prmoting substances and to the processes which normally regulate cell growth.