Changes in erythropoiesis and renal ultrastructure during exposure of mice to hypoxia.

During hypoxia, elevated ESF levels occur which are accompanied by increased erythropoietic activity resulting in progressive elevation of the haemoglobin and haematocrit concentration. An attempt has been made to correlate ultrastructural changes in the kidney with changes in serum ESF concentrations and the erythropoietic state of mice exposed to continuous hypoxia for 3 weeks. A series of changes in the epitheloid and proximal tubules cells occurred which may be related to the biogenesis of erythropoietin. However, no detectable ESF or renal erythropoietic factor could be extracted from the kidneys at the time of maximal ultrastructural changes. Although some ESF-inhibitory material was demonstrated, it could not be extracted into lipid solvents. It is suggested that the failure to consistently extract an erythropoietic factor from the kidneys of hypoxic mice may be related to the absence of renal storage at the onset of increased peripheral demand. Other levels and durations of hypoxia may help to elucidate the role of the kidneys in regulating serum ESF levels.