Radioautographic localization of the acetylcholine-stimulated synthesis of phosphatidylinositol in skin from patients with and without cystic fibrosis

Abstract

The distribution of radioautographic grains over various regions of human skin tissue was investigated after incubation of skin tissue slices for 2 hours in the presence of myoinositol-2- 3H with and without acetylcholine plus eserine. Skin tissue was obtained from control patients and from patients with cystic fibrosis, an inherited disease in which there is a defect in the function of all the exocrine glands, including the eccrine sweat gland. After incubation the skin slices were fixed in neutral formalin, washed in tap water, and embedded in a water-soluble wax (Carbowax). They were then sectioned and prepared for radioautography. Under these conditions only water-insoluble phosphatidylinositol (PI) should be radioactive. Labeling was found in the duct portion of the eccrine sweat gland as well as in hair follicles, epidermis, and some dermal areas when skin slices were incubated in the presence of myoinositol-2- 3H. It was randomly distributed throughout the cytoplasm of the cells; no nuclear labeling was seen. Only the duct region consistently gave a statistically significant increase in labeling when skin slices were incubated in the presence of myoinositol-2- 3H plus acetylcholine plus eserine. No labeling was found in the coil region of the eccrine sweat gland after incubation in the presence of myoinositol-2- 3H with or without acetylcholine plus eserine. No difference in the amount or distribution of label was observed between patients with cystic fibrosis and controls. Extraction of incubated tissue sections from control patients with both acidified and nonacidified chloroform: methanol prior to radioautography resulted in nearly complete removal of the labeling. In two of the three patients with cystic fibrosis, however, acidified chloroform: methanol was much more effective in removing label than was nonacidified chloroform: methanol. The possibility that the phosphatidylinositol effect found in the duct region of the eccrine sweat gland is related in some manner to the secretion and transport of ions and/or other materials across the duct is discussed.