Effects of glucose feeding, cortisol, and insulin on liver glycogen synthesis in the rat.

Abstract

To determine maximal rates of liver glycogen synthesis in vivo, normal, diabetic and adrenalectomized rats were fasted 48 hr, then were given repeated, heavy oral doses of glucose during a 16-hr period, then fasted 24–32 hr. Liver glycogen was assayed at regular intervals throughout these periods of glucose foeding and subsequent fasting. Normal rats synthesized liver glycogen at an extremely rapid rate of about 1% of fresh liver weight/hr to reach a peak of 16–18 % in 16 hr. Similar rates were observed in similarly fed 3-day cortisol-treated rats. Adrenalectomized rats displayed initially a slow rate of liver glycogen synthesis, but after a 2-hr lag period synthesized liver glycogen almost as rapidly as normal rats. However, the level “plateaued” at about 8–9 % after 8–10 hr. Similarly fed adrenalectomized rats treated with cortisol for 3 days responded exactly like normal rats. Similarly fed alloxan-diabetic rats, whose liver glycogen was depleted by prior glucagon injection, synthesized glycogen initia...