A glomerular defect in prehypertensive Dahl S rats, which limits their capacity to increase GFR

There is a great need to discover traits that predict future human hypertension. Our previous studies found abnormal glomerular filtration rates (GFRs) in isolated kidneys of Dahl S rats. Such GFR alterations were sought in intact, low NaCl, prehypertensive Dahl S rats. Such Dahl S rats are genetically susceptible to NaCl hypertension but are normotensive on low NaCl. On .3% low NaCl, BP of 12 Dahl S rats averaged 138 mm Hg v 131 in 12 Dahl R rats (NS). Glomerular filtration rates under inactin anesthesia were measured during two 20-minute periods before a 20-minute amino acid infusion and also during three 20-minute periods after the amino acid infusion. Before the amino acid infusion, GFRs averaged 3.3 mL/min in S rats v 3.25 in R rats (NS). After the amino acid infusion, R rats showed a progressive rise in GFR: 4.7, 5.1 and 5.4 in three successive 20-minute periods. In these same three periods after amino acids, the S rats had GFRs of 3.8, 3.8, and 3.8. Thus R rats had an 81% increase of GFR after amino acids, whereas S rats increased only 18%, a 78% lower increase, P less than .001. The R rats had the normal rise of GFR in response to an amino acid load. Prehypertensive S rats had virtually no increase in GFR after the amino acid infusion. Even though both S & R rats had BPs well within the normal range, the ability to increase GFR after amino acid infusion was markedly impaired in prehypertensive S rats. This defect could possibly be used to predict future hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)