Influence of starvation on sucrase regulation by dietary sucrose in the rat

Abstract

We have studied the action of sucrose on jejunal sucrase activity. Rats (175 g) were first starved or fed a digestible carbohydrate-free diet for 60 h and then fed a high sucrose diet for varying times up to 84 h. 1) Rats starved for 60 h showed mucosal atrophy with a decrease in protein content/10 cm (18.0 0 ± 1.4 versus 40.1 ± 3 mg (controls p < 0.001) and in villus height (357 ± 18 versus 526 ± 5 µm, p < 0.001) which was fully repaired only after 60 h on the sucrose diet (528 ± 11 µm). Rats on digestible carbohydrate-free diet showed no mucosal atrophy. 2) Starved rats had a delayed (60 h) sucrase activity response to sucrose (53 ± 7 versus 122 ± 4 µm/mg protein, p < 0.001). Maximum activity was obtained after 12 h on sucrose diet in rats maintained on the carbohydrate-free diet : 38 ± 1 versus 108 ± 2.3 µm/mg protein, p < 0.001. 3) Villus and crypt cell analysis after starvation and 12 h on a high sucrose diet localized the increase in sucrase activity to the villus-crypt junction. No change occurred in the upper villus. The increase was complete all along the villus by 36 h. In contrast, after the carbohydratefree diet, sucrase activity increased maximally at all levels of the villus by 12 h on the high sucrose diet. Thus starvation lowers villus height and renders the residual upper villus enterocyte incapable of responding to substrate, while elimination of digestible carbohydrate supports normal morphology and allows enterocytes to maintain their capacity to respond to sucrose by abruptly increasing their sucrase levels.