Describe the physiological consequences that follow an intravenous bolus of 50mls of
This question was mainly about the metabolic consequences of an intravenous load of 25
grams of glucose. For a good pass the main areas that required description included:
The transient glycosuria.
The mechanism and time course of the biphasic release of insulin from pancreatic cells.
The mechanism of the trapping of glucose within liver cells.
The multiple actions of insulin which include inhibiting glycogenolysis and promoting
glycgogen synthesis in the liver, promoting the uptake of glucose by muscle, fat and other
cells, increasing the metabolism of glucose to fatty acids and triglycerides, inhibiting
triglyceride breakdown and promoting protein synthesis.
Additional marks were awarded for details of where these actions of insulin occurred and the
enzymes that were stimulated or inhibited by insulin.
Some candidates stated that this bolus of hypertonic glucose would produce a significant and
prolonged increase in plasma osmolarity and then went on to produce detailed descriptions of
the thirst and ADH mechanisms. In fact with a normal insulin response glucose is rapidly
cleared from the blood.
Reference Text: Guyton Chp 67