Catecholamines in discrete kidney regions. Changes in salt-sensitive Dahl hypertensive rats

Steady state levels of catecholamines (dopamine, norepinephrine, and epinephrine) were measured by the use of radioenzymatic techniques in discrete areas of the kidney (outer and inner cortex, outer and inner medulla) dissected by a "punch" technique from frozen kidney sections of salt-sensitive (DS) and salt-resistant (DR) Dahl rats fed a low or high salt diet. All three catecholamines were present in all areas of the kidney examined. There were gradients of concentrations of each catecholamine in different kidney areas. Renal medullary areas contained proportionally more dopamine than cortical areas. The proportion of epinephrine with respect to the total catecholamine content was relatively high in the inner medulla. Genetic factors and the amount of dietary salt influenced the catecholamine content in specific kidney areas, and these changes were different according to the area considered. DS rats when fed a high salt diet presented increased systolic blood pressure but no increased levels of dopamine in the inner medulla nor of norepinephrine in the outer medulla and outer cortex. Results suggest that either the uptake, release, storage, synthesis, or catabolism of kidney catecholamines is altered in Dahl salt-sensitive (DS) hypertensive rats and suggest specific roles for each catecholamine in discrete areas of the kidney.