Renal disease and hypertension: the erythrocytosis factor

For some unknown reason, the blood hematocrit will become elevated 50 percent or more in some cases of renal disease where hypertension is a factor. In the absence of other identifiable causes of erythrocytosis, this is believed to result from the formation of erythropoietin stimulating factor (ESF) by the kidney in response to some intrarenal hypoxic stimulus. In this study it could be demonstrated with the help of computer simulations, that the hypertension was caused by excess fluid being retained by the kidneys, whereas, the elevated hematocrit could only be attributed to primary increase in the resistance to blood flow. This suggests that the high hematocrit levels that have been reported probably could not have occurred, except for powerful excess vasoconstrictor activity affecting the whole circulation.