AGING AS A FACTOR IN THE RENAL HEMODYNAMIC CHANGES INDUCED BY A STANDARDIZED PYROGEN

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Abstract
The renal hemodynamic response to an intraven. admd. pyrogen was detd. in 54 normal male subjects falling into 3 age groups: (Y) 20-49 yrs., (M) 50-69 yrs., and (O) 70-84 yrs. Admn. of aminopyrine before and during the test periods prevented the occurrence of chills and hyperpyrexia. The following effects of the pyrogen on renal hemodynamics were observed: (a) no changes in the glomerular filtration rate, (b) avg. increases of 71, 86, and 91% in the renal plasma flow for the Y, M, and O groups, respectively, (c) decreases in the filtration fraction from 0.189 to 0.115, 0.206 to 0.123, and from 0.232 to 0.122 for the Y, M, and O groups, respectively, and (d) decreases in the renal afferent and efferent hydraulic resistances in all age groups but greatest in the 70-84 yrs. group. From the results it is concluded that renal arteriolar dilation occurs in the aged individual. The significantly higher filtration fraction in the 70-84 yrs. group is predominantly the result of a physiologic mechanism and does not reflect an irreversible structural change in the arterioles.