Development of haemoglobin subtypes and extramedullary haematopoiesis in young rats. Effects of hypercapnic and hypoxic environment

The influence of repeated hypoxia on the development of haemoglobin (Hb) su btypes and on extramedullary haematopoiesis (EMH) was investigated in young Wistar rats of different ages. The rats were exposed to hypercapnic/hypoxi c and to "simple" hypoxic conditions. The results obtained were compared to those of an untreated age-matched control group. Different globin chains w ere measured using HPLC and time-of-flight (TOF) mass analysis. The number of EMH cells was evaluated by cell counting. By determining the proportions of alpha- and beta -chains, fetal, neonatal and mature types of globin cha in composition could be differentiated. The beta -2 chain levels were signi ficantly higher in hypercapnic/hypoxic environments than in the controls an d simple hypoxic environments. The numbers of EMH cells in the two groups s ubjected to hygercapnia/hypoxia decreased significantly mote slowly compare d to the controls and simple hypoxia groups. Therefore, the development of Hb subtypes and the EMT activity in rats were influenced by both repeated h ypercapnia and hypoxia.