Abstract
Continued subcutaneous administration of thyroxin is known to produce hyperglycemia. In normal sheep the blood-sugar is raised from about 70 mg. to over 80 mg.
A single subcutaneous administration of thyroxin has only a slight effect on the blood sugar.
A single subcutaneous administration of insulin (10 units) produced no demonstrable effect within two hours after injection.
Intravenous administration of varying amounts of insulin (5 to 15 units) produced prompt hypoglycemia in normal sheep, the sugar decreasing from about 70 to about 40 mgs. per 100 c.c. of blood within about 30 minutes. (No unfavorable symptoms were observed). The drop is regular, and when plotted is represented by a practically straight line. The slope of this portion of the curve is constant for the same sheep upon administration of varying amounts of insulin.
The portion of the curve representing recovery from hypoglycemia show characteristic differences : When 5 units of insulin were administered, the recovery to normal sugar values began immediately after the low values had been reached. With 10 to 15 units the minimum sugar values obtained were only slightly lower than for the smaller doses, although analyses were taken at sufficiently close intervals (10 to 20 minutes) to enable a fair approximation to the minimum. The larger doses, however, showed an extensive flat portion in the curves before recovery began. The results with five units were reproducible with the same sheep and similar in different sheep.
Five units were therefore selected as the standard dose of insulin to be tested against varying amounts of thyroxin under different conditions. Administered alone, the effects produced are represented by curves A and D. Curve G shows the effect of a preliminary administration of thyroxin (1 mg. intravenously). Curve C shows the effect of a similar injection of thyroxin after the recovery from insulin had begun. The simultaneous administration of thyroxin (1.5 mg.) and insulin produced a typical divergence of the ascending arm of curve E from that of curve D (insulin alone)
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