The Alteration of Intracellular Cyclic Nucleotides Levels during Stimulation on Erythropoiesis

In vivo and in vitro Studies

Abstract

We have analyzed the alteration of cyclic nucleotide levels in spleen and bone marrow after acetylphenylhydrazine (APH) -induced anemia. The studies were carried out on male Wistar rats. Rats received an intraperitoneal injection of acetylphenylhydrazine at a dose of 60 mg/kg body weight. Bone marrow and spleen cells were collected daily from the beginning to the recovery stage of anemia. The cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) levels were determined by radioimmunoassays. The spleen cAMP levels elevated gradually and showed the peak at 6 days after APH injection. The maximum level of bone marrow cAMP was found at 3 days after APH injection. A significant elevation of spleen cGMP level was detected and the maximum was shown at 5 days after APH injection. We have also analyzed the effects of erythropoietin (Connaught, step III) on cAMP levels of rat bone marrow cells suspended with RPMI 1640 medium containing 10% fetal calf serum at different times. Purified erythropoietin produced the increase of cAMP level in fractionated bone marrow cells when incubated with 10^-6 M theophylline (inhibitor to phosphodiesterase). It revealed that the increase of cAMP occurred shortly after adding erythropoietin in vitro. The relation between the initiation of erythropoiesis and increasing intracellular level of cAMP was discussed.