We investigated the importance of glucagon in the development of diabetic ketoacidosis by withholding insulin from six patients with juvenile-type diabetes and four totally pancreatectomized subjects. Patients were fasting and had previously been maintained on intravenous insulin for 24 hours. In diabetic patients plasma glucagon concentrations rose sharply after withdrawal of insulin, and the increases were accompanied by a rise in blood ketone concentration of 4.1+/-0.7 (S.E.M.) and blood glucose concentration of 12.5+/-1.8 mmol per liter by 12 hours. In the pancreatectomized patients, despite the absence of measurable glucagon, blood ketones rose by 1.8+/-0.8 and blood glucose by 7.7+/-1.5 mmol per liter. Thus, glucagon is not essential for the development of ketoacidosis in diabetes, as has previously been suggested, but it may accelerate the onset of ketonemia and hyperglycemia in situations of insulin deficiency.
Pre-operative bilateral simultaneous inferior petrosal sinus sampling with assessment of ACTH levels in the left and right sinuses and the periphery was performed in 9 patients with pituitary dependent Cushing's disease who were subsequently found at surgery to have basophil microadenomata. The novel observation of this study was the pattern of secretion of other pituitary hormones so that significant inter-sinus gradients \ m=ge\ 1.4:1 were seen for \g=b\-endorphin (2.8 \m=+-\1.3, mean \m=+-\ sem), PRL (4.2 \m=+-\ 1.3) and GH (6.9 \m=+-\2.4) as well as for ACTH (5.1 \m=+-\ 1.1). There was no inter-sinus gradient for LH, FSH and TSH. In these 9 patients with adenomata, the correlations between the inter-sinus gradients for ACTH and \g=b\-endorphin were r = 0.95 (P <0.01), ACTH and PRL r = 0.90 (P < 0.01) and for ACTH and GH r = 0.89 (P <0.05). This close association between the gradients for ACTH and other anterior pituitary hormones could be due either to cosecretion of \g=b\-endorphin, PRL and GH by the A C T H \ x = r e q -\ producingpituitary adenomata or to a paracrine effect of \g=b\-endorphin from the tumours on adjacent pituitary tissue. By reflecting the central pituitary hormone milieu, petrosal sinus sampling can give information about pituitary function unobtainable from peripheral hormone levels.
In order to determine whether glucagon levels of diabetic subjects are suppressible, alpha cell responsiveness to acute insulin administration (0.1 units/kg intravenously) was determined in fourteen juvenile onset, healthy diabetic and eight control subjects. In the diabetics, insulin produced a significant but slow fall in blood glucose over 60 min (P less than 0.01). On the other hand, glucagon levels fell dramatically in all diabetics to undetectable levels (P less than 0.001). Only one diabetic became hypoglycaemic and he alone showed a rebound rise of glucagon at 60 min. The rate of fall of blood glucose in the diabetic subjects was not influenced by the basal glucagon level (r=0.13) or the rate of fall of plasma glucagon (r=0.04). The glucose and glucagon responses of control subjects to insulin administration were in sharp contrast to the diabetics: blood glucose levels fell rapidly to hypoglycaemic levels and were associated with a major rise in glucagon levels (mean rise 116 pmol/1, P less than 0.001). We conclude that alpha cell hyperfunction in human diabetes can be completely suppressed by insulin administration and is therefore not autonomous, and that the slow rate of fall of blood glucose following insulin administration in diabetics is not secondary to glucagon excess.
The protein synthetic activities of membrane-bound and free hepatic ribosomes isolated from intact rats fed ad libitum, and normal rats subjected to food restriction to match that of hypophysectomised (Hx) rats were compared to the in vitro protein synthetic capacity of hepatic ribosomes isolated from Hx rats. Hypophysectomy resulted in decreased protein synthetic ability of bound ribosomes, whether protein synthesis was directed by endogenous messenger RNA (mRNA) (p less than 0.05) or by polyuridylic acid (polyU) (p less than 0.01). In contrast, the protein synthetic activity of free hepatic ribosomes from Hx rats was reduced when protein synthesis was directed by endogenous mRNA (p less than 0.05) but, when polyU was substituted as the messenger, the protein synthetic activity of these free ribosomes was equal to that of control rats. On the other hand the effects of food restriction on hepatic ribosomal function could be clearly differentiated from the effects observed following hypophysectomy. Thus, the reduced protein synthetic activity of hepatic bound ribosomes isolated from food restricted normal rats was not demonstrable, when polyU was used to direct protein synthesis. Further, food restriction had no effect on the protein synthetic activity of free hepatic ribosomes, and this was true when protein synthesis was directed by either endogenous or artificial messenger. It is concluded that hypophysectomy reduces the protein synthetic ability of both bound and free hepatic ribosomes, and this change of ribosomal function of Hx rats cannot be attributed to their decreased food intake.
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