Reduced extrarenal erythropoietin production in rats treated with isoproterenol.

Erythropoietin production was studied in 30-day-old and adult rats previously injected with pharmacological doses of isoproterenol. The animals were stimulated either by hypobaric hypoxia or by a combination of hypoxia and acute anemia. The erythropoietic activity of the plasma was measured by 59Fe incorporation in total circulating red blood cells of mice made polycythemic by chronic hypoxia. The results were converted to units of erythropoietin (IRP). A significant reduction of erythropoietin production was observed only in young rats. Our interpretation of the findings is that isoproterenol induced the differentiation of the salivary glands in the young animals hence reducing hormone production at the extrarenal (submandibular) level.