Role of cholesterol in the structure and function of gastric microsomal vesicles

✍ Scribed by Tushar K. Ray; Jyotirmoy Nandi; Andrew Dannemann; Gerald B. Gordon

• Publisher: John Wiley and Sons
• Year: 1983
• Tongue: English
• Weight: 653 KB
• Volume: 21
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.240210205

✦ Synopsis

Digitonin was used as a tool to investigate the organization and function of cholesterol in gastric microsomes. Microsomal vesicles were treated with digitonin for different time at 04°C under isotonic conditions. The effects of digitonin treatment of the vesicles on removal of cholesterol, ultrastructural changes, (H+ + K+)-ATPase activity, and gastric ATPasedependent H+ uptake ability were investigated. Microsomal cholesterol was extracted in an exponential manner with a t1/2 of 32 min. There was no release of microsomal phospholipids by digitonin treatment during the same period. Digitonin treatment (30 min) produced visible "holes" in the vesicles; at the same time (H+ + Kf)-ATPase-dependent H+ uptake was abolished. Under the same conditions the K+-stimulated ATPase activity, however, was moderately (about 35 %) reduced, although the response of K+ stimulation to valinomycin was obliterated. Longer digitonin treatment resulted in gradual diffusion and eventual disappearance of the "holes" with the generation of distorted cup-shaped microsomes. The data strongly suggest that membrane lipids are freely mobile and that there is a certain degree of specialization in the organization of gastric microsomal cholesterol for the proper maintenance of the membrane structure and function.

Key words: gastric microsomal vesicles, membrane cholesterol, digitonin, H+ , K+-ATPase, vesicular H+ transport Cholesterol and phospholipids are the two primary lipid components of the animal cell plasma membranes. Although significant progress has been made in recent