FACTORS AFFECTING THE INSULIN CONTENT OF THE PANCREAS

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Abstract
The insulin level found in the pancreas depends upon the methods used for assay. It fluctuates with the age of the animal, with ligation of the pancreatic ducts or extensive partial pancreatectomy, with the adm. of alloxan or certain ant. pituitary extracts, and with unknown factors; but not much with the sp. of animal, with barbiturate anesthesia, nor with infection. The evidence seems to support the view that fasting, fat-feeding and insulin adm. reduce the need for endogenous insulin and lower the insulin content of pancreas by making the islet cells less active. The lowering must result from a diminution in production relative to any change in liberation On the other hand, the great increase in islet stimulation resulting from the inj. of ant. pituitary extracts or partial pancreatectomy probably leads to exhaustion of the [beta] cells through overwork. The lowering of the insulin content of pancreas here would seem to result from an increase in the liberation of insulin that is out of proportion to any change in the production of that material. The factors primarily responsible for the stimulation of the [beta] cells of the islets are not clearly established. Some contend that the blood sugar level plays the chief part in this regulation; others believe that the blood insulin level may be involved. The nervous system has only a minor role. While the fundamental control of the insulin content of the pancreas is not dependent upon the pituitary, adrenals, or gonads, nevertheless, under certain exptl. conditions, it would appear that a pituitary effect may be superimposed upon the essential mechanism. It has not been demonstrated that such a direct pituitary influence operates in the normal animal, but if it does it would provide for an additional increase in the secretion of insulin when the need is great. The evidence indicates that, in exptl. animals, several means are available for reducing islet stimulation and lessening the strain on the [beta] cells. There is reason to believe that the same procedures are effective also in man. While it is true that by their use islet damage can be prevented and the [beta] cells restored, yet their excessive application may lead to poor nutrition of the animal and, in some instances, to atrophy of the islets. Since excessive "rest" may be as undesirable as excessive stimulation, discretion must be used in the clinical application of these findings.