An abrupt reduction of medium osmolarity by as little as 20 mosM evoked a discrete short-lived insulin secretory response from perifused chopped pancreas or isolated islets. The insulin response occurred earlier than that induced by either glucose or tolbutamide. None of the usual modifiers of insulin secretion significantly altered this secretory response. Glycolytic inhibitors, adrenergic agonists and blocking agents, cholinergic blocking agents, mitotic spindle inhibitors, and agents influencing sodium pump activity failed to alter hyposmolar-induced insulin secretion. Manipulation of the perifusion medium calcium concentration was the only procedure tested that influenced the secretory response. Perturbations of medium calcium concentration that increased the tissue-to-medium calcium gradient augmented the hyposmolar-induced insulin response and those that decreased tissue-to-medium calcium gradient greatly inhibited the response. The precise cause of the insulin response to a decrease in bathing fluid osmolarity remains undefined; however, the stimulus is not specific for insulin because increases in glucagon and amylase were also elicited by the hyposmolar stimulus.

To evaluate the role of serum calcium in human insulin secretion, insulin responses after a 100-g oral glucose load were studied in nine patients with primary hyperparathyroidism, five with idiopathic hypoparathyroidism, three with pseudohypoparathyroidism and one with normocalcemic secondary hyperparathyroidism. Glucose tolerance values in these disorders were almost normal. Insulin responses in primary hyperparathyroidism were increased, and those in idiopathic hypoparathyroidism and pseudohypoparathyroidism were reduced significantly as compared to normal subjects. Isulin response in secondary hyperparathyroidism was normal. The calculated insulin area during an oral glucose load was significantly correlated with serum calcium (5.1 to 12.2 mg per deciliter), and a linear relation was obtained (y = 1.59x - 3.3, r = 0.81, p less than 0.001), although a relation with the glucose area was not found. These observations indicate that serum calcium has an important effect on insulin secretion in parathyroid disorders.

The shape and size of the adrenals in control subjects without adrenal disorders were studied by computed tomography (CT), and a comparative assessment of diagnostic values of ultrasonography (US) by electronic linear scanner, CT, and adrenal scintigraphy was made on 9 patients with primary aldosteronism. Adrenal imaging by scintigraphy was performed on the 5th and 6th day, or further on the 7th day after the injection of 1 mCi of Adosterol. CT findings of the adrenals in control subjects: Eighty-two % of 100 control right adrenals, and 89% of 100 control left adrenals were detected by CT. Seventy-seven % of the right adrenals were in linear-shape, and the others were in V-shape. The shape of the left adrenals could be classified into triangular-shape (54%), Y-shape (28%) and V-shape (18%). The mean width and thickness of the right adrenals were 28.6 +/- 7.5 mm (M +/- SD) and 3.8 +/- 1.4 mm, respectively. Those of the left ones were 19.4 +/- 5.5 mm and 5.3 +/- 1.8 mm. Image diagnosis of primary aldosteronism: In 2 out of 3 patients examined by US, aldosteronomas were detected. In these 2 patients, one had 2 adenomas 2.8 X 1.7 X 1.2 cm and 1.0 X 1.0 X 2.0 cm in size, and the other had one adenoma 0.8 X 1.0 X 2.0 cm in size. On adrenal scintiscanning under dexamethasone pretreatment (DP), the isotope uptake of aldosteronoma was still seen with the disappearance of the contralateral adrenal in 7 out of 9 cases. In these 7 cases, the laterality of the tumor was confirmed. In one of the remaining 2 cases, the bilateral adrenal images were obtained regardless of DP. In the other case, of which aldosteronoma was the smallest (0.6 X 0.6 X 0.8 cm), the image of the affected adrenal with adenoma as well as the contralateral adrenal disappeared under DP. CT delineated all aldosteronomas in 8 cases examined including 2 cases in which adrenal scintiscanning failed to elucidate the localization of aldosteronoma. These results indicated that the combination of these 3 new image diagnostic methods was available for the detection of aldosteronomas of various sizes.

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Physiological amounts of glucagon replacement brought about the reduction of plasma branched chain amino acid levels as well as glucogenic amino acid levels in a totally pancreatectomized patient who was under a steady feeding state, i.e., constant administration of an elemental diet combined with continuous subcutaneous insulin infusion. This finding suggests that glucagon may play a physiological role not only on glucogenic amino acids but also branched chain amino acids in plasma in feeding state.