Enhanced effect of increased erythrocyte production rate on plasma erythropoietin levels of mice during subsequent exposure to hypobaria.
The present study was undertaken to determine plasma EPO levels in response to acute exposure to hypobaria in transfused-polycythemic mice previously exposed to different forms of erythropoietic stimulation. The erythrocyte production rate (EPR) was stimulated by one of the following conditions: (1) discontinuous exposure to 456 mb during 4 weeks, (2) one weekly injection of phenylhydrazine (PHZ) during 4 weeks for induction of a compensated hemolytic state, and 3) three weekly injections of rHuEPO at a dose level of 1500 U/Kg body weight for 4 weeks. Treated and control mice received different volumes of packed red cells in order to obtain hematocrit values around 65% in all groups. Mice from each group were exposed to 456 mb during 14 h, 4 days after transfusion. Mice were bled immediately through cardiac puncture after removal from the hypobaric chamber. Plasma EPO titer was estimated by radioimmunoassay. Two observations were worth noting: (1) plasma iEPO level was very low in mice with transfusion polycythemia exposed to hypobaria, the value of 12 +/- 1.3 mU/ml being significantly different from that of 180 +/- 18 mU/ml found in normocythemic mice similarly exposed, and (2) plasma iEPO levels during EPRs were previously stimulated by different conditions (hypobaria, PHZ and rHuEPO) were at least as high as those found in normocythemic mices similarly exposed. All these values were significantly higher than the value corresponding to polycythemic mice whose EPRs were not stimulated before exposure to hypobaria.(ABSTRACT TRUNCATED AT 250 WORDS)
Bozzini
C E
CE
Department of Physiology, Faculty of Odontology, University of Buenos Aires, Republica Argentina.
Alippi
R M
RM
Barcelo
A C
AC
D000818:Animals; D001273:Atmosphere Exposure Chambers; D001274:Atmospheric Pressure; D001803:Blood Transfusion; D004920:Erythropoiesis / Q000187:drug effects; D004921:Erythropoietin / Q000097:blood* / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D006400:Hematocrit; D051379:Mice; D010659:Phenylhydrazines / Q000494:pharmacology; D011086:Polycythemia / Q000209:etiology / Q000503:physiopathology*; D011994:Recombinant Proteins / Q000494:pharmacology; D012636:Secretory Rate / Q000187:drug effects
D010659:Phenylhydrazines; D011994:Recombinant Proteins; C030299:phenylhydrazine; D004921:Erythropoietin