On the role of renal alpha-adrenergic receptors in spontaneously hypertensive rats.

We tested the hypothesis that a genetically determined increase in renal alpha-adrenergic receptor density might be a pathophysiologically important factor in the spontaneously hypertensive rat model of genetic hypertension. In a first study, we compared renal alpha 1 and alpha 2-adrenergic receptor density with systolic blood pressure in 45 rats of an F2 generation of Wistar-Kyoto x spontaneously hypertensive rat hybrids but were unable to detect significant cosegregation between either receptor density or blood pressure. In a second study, we determined renal alpha 1- and alpha 2-adrenergic receptor density in Wistar-Kyoto and spontaneously hypertensive rat kidneys that were transplanted into an F1 generation of Wistar-Kyoto x spontaneously hypertensive rat hybrids. Although Wistar-Kyoto kidneys lowered blood pressure in these animals and spontaneously hypertensive rat kidneys increased blood pressure, renal alpha-adrenergic receptor densities were similar in membranes from both types of kidneys. Since rat kidney coexpresses alpha 1A- and alpha 1B-adrenergic receptors, we also investigated whether differential regulation of these two subtypes might conceal ongoing alterations. The alpha 1A/alpha 1B-adrenergic receptor ratio, however, was similar in Wistar-Kyoto rats, spontaneously hypertensive rats, and F1 rats transplanted with a kidney from either strain. Taken together these data do not support the hypothesis that genetically determined alterations of renal alpha-adrenergic receptor numbers play an important role in the development of elevated blood pressure in the spontaneously hypertensive rat.