Summary

The haemoglobins of Xenopus laevis have been studied by carboxymethyl-cellulose column chromatography and by polyacrylamide gel disk electrophoresis. In Xenopus tadpoles, 2 haemoglobins are found (Xenopus-HbF₁ and Xenopus-HbF₂). Both haemoglobins persist throughout tadpole life: Xenopus-HbF₁ is the main tadpole haemoglobin; Xenopus-HbF₂ is present in rather smaller amounts. The proportion of Xenopus-HbF₁ to Xenopus-HbF₂ increases as the tadpoles age. Almost all the tadpole haemoglobin disappears soon after metamorphosis, although traces persist throughout adult life. Two adult haemoglobins occur in Xenopus: they first appear during the later tadpole stages. Xenopus-HbA₁ comprises the majority of the adult haemoglobin. Between one-twentieth and one-tenth of the adult haemoglobin consists of Xenopus-HbA₂, which is not a polymer of Xenopus-HbA₁

Immunoglobulins respectively specific to pooled Xenopus-HbF₁ and Xenopus-HbF₂, and to pooled Xenopus-HbA₁ and Xenopus-HbA₂ were raised. Samples of these antibodies were conjugated with fluorescein isothiocyanate.

Adult Xenopus were made anaemic by bleeding or by injection of phenylhydrazine. Fourteen days after the induction of anaemia it was found, using both chromatographic and electrophoretic techniques, that most anaemic toads had started to resynthesize Xenopus-HbF₁. In some animals up to 11% of the haemoglobin present was found to be Xenopus-HbF₁, and precipitin lines were obtained when the pooled haemoglobins from these animals were tested with a specific anti-Xenopus-HbF immunoglobulin. During recovery from anaemia greatly enhanced amounts of Xenopus-HbA₂ (up to 58% of the total haemoglobin) were present in the blood. The amounts of tadpole haemoglobins present in such recovering toads were not noticeably greater than in healthy animals. Between 42 and 120 days after the induction of anaemia the haemoglobin profile of the toads regained normality.

Blood cell smears were made from anaemic toads which were known to possess abnormal amounts of Xenopus-HbF₁ 14 days after the induction of anaemia. The smears were treated with specific anti-Xenopus-HbF immunoglobulin conjugated with fluorescein isothiocyanate. Although up to 11% of the haemoglobin present in the animals was Xenopus-HbF₁, the number of fluorescing cells was no greater than in similarly treated smears from healthy control adults possessing less than 1% Xenopus-HbF₁

It is concluded that during anaemia Xenopus starts to resynthesize one of its tadpole haemoglobins. This resynthesis occurs in many or most of the circulating red cells, and is not confined to a small population of cells. During recovery from anaemia enhanced quantities of Xenopus-HbA₂ are made.