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Postabsorptive plasma concentrations of citrate, glucose, lactate, free fatty acids (FFA), ketone bodies and free insulin were measured once weekly for 5 weeks in 18 male juvenile diabetics. The circadian rhythms of the same substances were followed in 12 male diabetics. In 8 of them, daily rhythms were measured twice, before and after plasma glucose was lowered by increasing insulin doses. In the postabsorptive state, the mean plasma citrate concentration of the diabetics, 117 mumol/l (range 65--160), did not differ from that of non-diabetics despite two- to threefold higher levels of plasma glucose, FFA and ketone bodies in diabetics. Daily plasma citrate profile in diabetics showed peak concentrations in the morning and late afternoon. Citrate level throughout the day fell after increased insulin administration, whereas the diurnal pattern remained unchanged. Both the week-to-week coefficient of variation (mean 10%) and the diurnal coefficient of variation (mean 17%) of plasma citrate were below those of any other substances measured (p less than 0.001). Postabsorptive citrate concentration correlated negatively to the diurnal variation of plasma glucose whether diabetic control was apparently good or poor. The results support the idea that plasma citrate level reflects intracellular citrate regulation of glucose utilization. In spite of an interindividual range of 100%, individual citrate level was remarkably constant. Postabsorptive plasma citrate concentration is proposed as a control marker of lability of circulating glucose in insulin-treated diabetics.

We present the case histories of two patients with angina pectoris who developed coronary artery spasm in response to provocation with prolonged hyperventilation (verified by ST segment elevation in both and coronary angiography in one) despite a negative ECG response to intravenous injection of 0.4 mg ergometrine. This new observation, which is in conflict with recent publications stating that ergot provocation is more sensitive than hyperventilation, suggests that in some patients diagnostic provocation with hyperventilation may be an alternative to the widely used ergot provocation.

We studied the exercise stress test and the coronary artery tone in two groups of angina patients with comparable coronary atherosclerosis. Group I (20 males and 5 females, mean age 53.5 years) with a positive, and group II (22 males and 3 females, mean age 52.5 years) with a negative response to the hyperventilation test (HVT). A positive exercise stress test (ST depression greater than or equal to 1 mm) was found in 24 patients in group I vs. 15 in group II (p less than 0.01), despite a lower maximal rate pressure product (198 +/- 11.2 vs. 236 +/- 10.1, p less than 0.05) and maximal work load (110 W +/- 7.1 vs. 136 +/- 7.4 W, p less than 0.02) in group I. A high coronary artery tone (dilatation (DIL%) of the coronary arteries after nitroglycerin greater than or equal to 10%) was found in 18 patients in group I and in 4 in group II (p less than 0.01). DIL% was 22.6 +/- 3.8 vs. 5.8 +/- 1.4 in groups I and II, respectively (p less than 0.005). DIL% was significantly related to persistence of ST depression after exercise (r = 0.36, p less than 0.05), and 21 of 22 patients with high tone had a positive exercise stress test vs. 18 of 28 with low tone (p less than 0.05). These findings suggest that the coronary artery tone influences the response to exercise in some patients with angina. Since the patients in group I were identified by HVT, our results underline the clinical relevance of this test.