Comparative Study of the Development of Alkaline Phosphodiesterase I and Alkaline Phosphatase in Mucosa of Rat Jejunem and Ileum

Abstract

During the early postnatal period phosphodiesterase I is almost equally distributed in the jejunum and the ileum of rat intestine. By the end of the third week after birth the specific activity in the jejunum decreases to about one-half and in the ileum to about one-tenth of the activities found on the ninth day, forming a proximo–distal gradient typical of adult animals. The activity of alkaline phosphomonoesterase in newborns is much lower than that of phosphodiesterase I and increases rapidly the first day. During the second week the specific activity of alkaline phosphatase in the ileum rises to more than double that in the jejunum and the final proximo–distal gradient is established somewhat later. For both enzymes the amount of activity appearing as soluble cytoplasmic material is highest in newborn rats and diminishes as the animals mature. The extractibility of activity from the insoluble microsomal fractions with Triton X-100 follows the same trend. After extraction of the enzymes from microsomes by treatment with tert-amyl alcohol, Triton X-100, or glycerol, most of the phosphodiesterase I activity appears in large complexes of molecular weight of several millions, but after autolysis the complexes break down to molecules of molecular weight close to 150 000 without appreciable loss of activity.