KIDNEY CROSS TRANSPLANTS IN DAHL SALT-SENSITIVE AND SALT-RESISTANT RATS

Previous kidney cross-transplant studies have demonstrated that the genotype of the kidney plays a role in determining the blood pressure of the recipient in Dahl salt-sensitive (S) and salt-resistant (R) rats. The present studies were designed to elucidate this role. Kidney cross transplants were performed in unilaterally nephrectomized male recipients (John Rapp strains), such that each rat had a native kidney and a transplanted kidney of the opposite genotype. S and R rats with a native kidney and a transplanted kidney of the same genotype served as controls. After 4 wk on a 7.8% NaCl diet, rats were anesthetized and renal clearance studies were performed. S kidneys had lower glomerular filtration rate (GFR) and renal plasma flow (RPF) than R kidneys, and these differences were determined by the kidney's genotype rather than the recipient's since S kidneys in R recipients tended to have lower GFR and RPF than R kidneys in S recipients. In contrast, independent of the kidney's genotype, the kidneys in S rats tended to have higher fractional excretion of H2O and Na (FE(H2O) and FE(Na)) than the kidneys in R rats. Thus there were genetically determined differences in renal function between S and R rats; some (RPF and GFR) were intrinsic to the kidney, whereas others (FE(H2O) and FE(Na)) were intrinsic to the host. Extrapolation of these results to bilaterally nephrectomized recipients might explain the previous findings of others; i.e., an R recipient (genetically programmed for low FE(H2O) and FE(Na)) of an S kidney (genetically programmed for low GFR) would become volume expanded and blood pressure would increase, whereas an S recipient (high FE(H2O) and FE(Na)) of an R kidney (high GFR) would become volume depleted and blood pressure would decrease.