The effects of α2-adrenergic-receptor blocker mianserin on the responses of blood glucose, plasma β- thromboglobulin (β-TG), and various counterregulatory hormones to insulin-induced hypoglycemia were studied in nine healthy male subjects. The α2-adrenoceptor- blocking action of mianserin was confirmed by its inhibitory effect on platelet activation in vitro. Mianserin was given orally 90 min before insulin injection; the same study without mianserin was performed on another day as the control study. The time courses of blood glucose and serum C-peptide (0, 20, 45, and 180 min after the insulin injection) were identical in both studies, indicating that mianserin has no effect on these parameters. However, a significant increase of p-TG at 45 min after insulin injection was completely suppressed by the administration of mianserin (mean ± SE, 68.5 ± 6.0 vs. 28.8 ± 7.6 ng/ml, n = 6, P < .05). No significant differences were obtained between the two studies in the responses of plasma or serum catecholamines, cortisol, glucagon, growth hormone, thromboxane B2, and 6-ketoprostaglandin F1a. These results suggest that epinephrine is responsible for some, if not all, of the β-TG release from the platelets during insulin-induced hypoglycemia.

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