SUMMARY
1. Microsomes, isolated from rat liver a day after adrenalectomy, incorporate more radioactive amino acid into their protein in vitro than microsomes from normal rat liver. This enhanced rate of incorporation progressively declines with time after adrenalectomy until it reaches a plateau level which is below the normal rate of incorporation.
2. Following adrenalectomy microsomes isolated from liver of male rats show a greater rise in incorporating ability than those from liver of female rats, and maintain it longer.
3. Most of the increased incorporation observed in the in vitro system soon after adrenalectomy of the rat, and most of the decreased incorporation observed in rats adrenalectomized for some time, results from alterations in the microsomes which change their ability to incorporate activated amino acids into proteins.
4. Treatment of rats with cortisol acetate results in an increase in the ability of liver microsomes to incorporate amino acid into protein. This heightened incorporating ability is probably a secondary result of the breakdown of extrahepatic tissue protein which is stimulated by cortisol.
5. Somewhat similar responses to acute adrenalectomy and to treatment with cortisol were found in hypophysectomized rats.
6. The protein anabolic response of adrenalectomized rats to treatment with insulin, and of adrenalectomized-hypophysectomized rats to treatment with insulin or growth hormone, is greater than that shown by rats which possess adrenal glands.
Further Studies on the Amino Acid Incorporating System of Rat Liver Microsomes