Krister Fredén

The Exchangeable Splenic Platelet Pool in Response to Selective Adrenergic Beta‐1‐Receptor Blockade

The aim of the present work was to investigate the effect of selective beta‐I‐blockade on the exchangeable splenic platelet pool (ESPP). Therefore, 50 mg of metoprolol (a selective beta‐i‐receptor blocking agent) was given by mouth to three groups of subjects: (1)15 healthy volunteers, (2) five asplenic subjects, and (3) 10 patients with different myeloproliferative disorders (MPD) with and without splenomegaly. The platelet count was determined 90, 150, 210, 270 and 330 min after the ingestion of the drug.

Peripheral Platelet Count in Response to Salbutamol Before and After Adrenergic Beta-Receptor Blockade

The effect of salbutamol (a comparatively selective adrenergic beta2-receptor agonist) on the peripheral platelet concentration was studied before and after the ingestion of either 50 mg metoprolol or 40 mg propranolol. The study was carried out on healthy males volunteers and autologous 51Cr-labelled platelets were employed at the experiments. Salbutamol was infused intravenously over a period of 6 min in a dose of 0.27 microgram.kg(-1). min(-1). Prior to metoprolol and propranolol administration a statistically significant lowering in platelet-bound radioactivity (PBR) was obtained in response to the salbutamol infusions. This salbutamol-induced fall in PBR was completely blocked by propranolol but was left unaffected by metoprolol. It is concluded that adrenergic beta2-receptor stimulation induces a transient lowering of the peripheral platelet count.