Sympathomedullary activity in one-kidney, one clip hypertensive rats

In order to evaluate more directly the implications of the sympatho-adrenal system in one-kidney, one clip hypertension (1K1C), we studied adrenal catecholamine synthesis after a bolus injection of 3H-tyrosine, tissue norepinephrine and dopamine concentrations, as well as the urinary excretions of norepinephrine, epinephrine, dopamine and those of the major dopamine metabolites, dihydroxphenylacetic acid (DOPAC) and homovanillic acid (HVA) in 1K1C and control uninephrectomized rats. When compared with controls, the hypertensive rats had a markedly enhanced formation of adrenal 3H-norepinephrine and 3H-epinephrine, higher urinary norepinephrine and epinephrine excretions but lower heart and kidney content of norepinephrine and dopamine as well as decreased urinary excretions of the main dopamine metabolites, DOPAC and HVA. These data suggest an increased norepinephrine and epinephrine synthesis in 1K1C hypertensive rats associated with dopamine synthesis, which is normal but probably disproportionally low relative to the synthesis of norepinephrine and epinephrine. This abnormality may be an important pathogenetic factor in this model of experimental hypertension.