KALLIKREIN EXCRETION IN DAHL SALT-SENSITIVE AND SALT-RESISTANT RATS WITH NATIVE AND TRANSPLANTED KIDNEYS

Urinary kallikrein excretion is decreased in Dahl salt-sensitive (S) v s. salt-resistant (R) rats, and several lines of reasoning suggest not only that decreased kallikrein excretion is a marker for salt-sensiti ve hypertension but also that kallikrein might play a pathogenic role. Because previous cross-transplantation studies have demonstrated that the kidney's genotype plays a role in determining the blood pressure of the recipient in Dahl S and R rats, the present experiments were de signed to determine whether both blood pressure and urinary kallikrein excretion ''traveled with the kidney'' in transplantation. The Rapp s trains of S and R were maintained on a low- NaCl (0.13%) diet until ki dney transplantation (bilaterally nephrectomized recipients), at which time the diet was switched to high NaCl (7.8%). Sixteen days later, b lood pressures (tail-cuff plethysmography) of the cross-transplant gro ups (R/S and S/R, indicating kidney genotype/recipient genotype) were nearly identical to each other and intermediate between the blood pres sures of the control groups with transplanted kidneys (R/R and S/S). R enal function studies, performed on anesthetized rats 17 days after su rgery, demonstrated that R kidneys had higher glomerular filtration ra tes, renal plasma flows, and urinary kallikrein excretion rates than S kidneys. These differences tended to be preserved in the cross-transp lant groups, and therefore they must be genetically determined intrins ic differences between R and S kidneys. This was especially striking w ith respect to urinary kallikrein excretion. The rank order of urinary kallikrein excretion was R/R = R/S > S/R = S/S, which implies that it is completely determined by the genotype of the kidney. Finally, alth ough these intrinsic differences between the kidneys might play a role in determining blood pressure, they cannot be the entire explanation, because blood pressures in the cross-transplant groups were nearly id entical. Thus, in conclusion, extrarenal genetic factors in the recipi ent also have a decisive role in control of blood pressure.