Plasma insulin content in relation to blood glucose level and meal pattern in the normal and hypothalamic hyperphagic rat

In the food deprived VMH hyperphagic animal the glucose level is comparable to that in the deprived intact animal, but the insulin response is also in this case very exaggerated.

Abstract

Blood samples were withdrawn at short intervals from unanesthetized rats by means of a chronic intracardial cannula. Glucose and insulin levels were determined. Accurate records were kept of the time pattern of feeding in these animals, whose normal behavior was not disturbed at all by the sampling procedure. In thead libitum situation, the start of a meal entails a rise of the glucose level within two min. This culminates in a peak within 15 min which is followed by a rapid return to pre-meal levels. Insulin is very low (25 μU/ml plasma) before the meal, rises rapidly after its start, and then declines to values markedly above pre-meal levels. (66 μU/ml plasma). In the VMH hyperphagic animal the glucose level is comparable to that in the normal animal but the insulin level is exceedingly elevated. After 24 hr of food deprivation, the glucose level of the intact subject has dropped to about 80 mg % and insulin to 10–20 μU/ml plasma. When food is returned, glucose rises rapidly within one minute after the start of the first meal. Insulin goes up, but attains a much lower peak level than underad libitum conditions, and declines again to very low values (35.5 μU/ml plasma). In contrast, glucose remains relatively high. In the food deprived VMH hyperphagic animal the glucose level is comparable to that in the deprived intact animal, but the insulin response is also in this case very exaggerated.