The peripheral utilization of glucose in the rat and domestic fowl



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The peripheral utilization of glucose was assessed in the rat and domestic fowl following injection of the g-cell cytotoxins alloxan and streptozotocin. Additionally, the effect of partial pancreatectomy (99%) on previously streptozotocin- treated chickens was investigated. The measurement of basal plasma glucose, plasma immunoreactive insulin (TRI) and plasma electrolytes (in the fowl) was made to assess the diabetogenicity of these chemical agents. Glucose tolerance tests (GTT) were administered to measure the disposal of a carboydrate challenge and the accompanying insulin secretory profile. The responsiveness of insulin-secreting tissue to tolbutamide (an insulin-releasing agent) was investigated both in 15-day streptozotocin chickens and in the doubly-treated chickens (streptozotocin plus surgical extirpation (99%) of the pancreas). The results of this study indicate that alloxan and streptozotocin injection in the rat induced quantitatively similar metabolic disturbances. The virtual depletion of basal plasma IRI levels was approximately the same in both groups; the incipient hyperglycemia, too, was approximately the same in the streptozotocin-injected rats and the alloxan group. An increase in plasma glucose of 268% was observed in the former and 251% in the latter. The glucose-induced insulin secretory response was a flat, hyporesponsive curve in both groups. Alloxan administration to the chicken was without effect on basal plasma glucose concentration or basal IRI levels. Additionally, alloxan was without effect on glucose- induced insulin secretion or the peripheral utilization of glucose. Electrolyte balance in the alloxan-treated chicken was undisturbed. Peripheral utilization of glucose in the streptozotocin- injected bird remained unimpaired while the glucose-induced insulin secretory profile was significantly less than that of the normal control. Basal plasma glucose, plasma IRI and electrolytes were all normal. The doubly-treated fowl (streptozotocin plus pancreactomy) exhibited both normal fasting plasma sugar concentration and plasma IRI. In response to a GTT, however, the glucose-induced insulin secretion was identical to streptozotocin treatment alone. Yet an impaired removal of the injected glucose load was evident at 60 minutes following the glucose challenge and so remained for the duration of the GTT observation period. Sodium tolbutamide injection immediately following the 3 hour GTT elicited an identical increase in plasma IRI levels (250- 325%) in all groups, yet the impaired glucose tolerance remained in the doubly-treated fowl. [...]