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f liver ►i muscle t fat brain figure 7-26 Comparison of the relative contributions of insulin and glucagon to the maintenance of blood glucose homeostasis in (A) normal basal state; (B) an instance of exercise; and (C) after ingestion of a carbohydrate-rich meal. (A) The role of glucagon in maintaining glucose influx at a rate equal to that of glucose efflux into insulin-independent tissues so as to maintain the extracellular fluid (ECF) glucose concentration above a hypoglycemic range is emphasized. (B) The role of glucagon in maintaining glucose influx equal to markedly increased glucose efflux into exercising muscle so as to maintain the ECF glucose concentration above a hypoglycemic range and maintain cerebral glucose delivery is emphasized. (C) The role of insulin in increasing glucose efflux during the rapid influx of ingested glucose so as to prevent an abnormal rise in ECF glucose is emphasized. Reduced glucagon secretion may facilitate this by helping to diminish hepatic glucose production. [Reproduced with permission from Unger, R. H., and Orci, L. (1979). Glucagon and diabetes. In "Endocrinology" (L. J. DeGroot et ah, eds.), Vol. 2, p. 962. Grune & Stratton, New York.l

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