Background

Dysfunctional dopamine neurotransmission and greater than normal retention of salt have been found for renal proximal tubules of the spontaneously hypertensive rat.

Objective

To determine whether there are differences between kidney D1 A dopamine receptor distributions of spontaneously hypertensive rats and Wistar–Kyoto rats.

Methods

We examined the expression of D1 A dopamine receptors in kidneys of spontaneously hypertensive rats and the normotensive Wistar–Kyoto rat through Western blots and immunocytochemistry, using highly specific antipeptide antibodies directed against the receptor.

Results

The specificity of the antisera was demonstrated by Western blot studies, using proximal tubules, from Wistar–Kyoto rats. The antiserum recognized a major polypeptide with M r of 72 kDa and a minor protein of M r 66 kDa, which were not detected either by antigen-adsorbed or by preimmune sera. In renal cortex of both Wistar–Kyoto rats and spontaneously hypertensive rats, D1 A receptors were expressed at equivalent levels. In the inner medulla of Wistar–Kyoto rat, there was diminished (by 60%) expression of D1 A receptors compared with that of the renal cortex. However, the expression of D1 A receptors in the inner medulla in the spontaneously hypertensive rat was even more diminished (by 83%) relative to levels found in spontaneously hypertensive rat renal cortex. Immunocytochemical studies localized the D1 A receptor protein in renal cortex primarily to epithelia of tubules. Relative to renal cortex, there was an overall decrease in staining intensity in the inner medulla both of Wistar–Kyoto rats and of spontaneously hypertensive rats. Compared with that of Wistar–Kyoto rat, the intensity of staining of D1 A receptors in the inner medulla of spontaneously hypertensive rats was greatly diminished, confirming the Western blot analyses. The less than normal expression of D1 A receptors in the inner medulla of spontaneously hypertensive rats might be of physiologic importance in the etiology of greater than normal retention of salt and hypertension in spontaneously hypertensive rats. J Hypertens 16: 601–608© 1998 Lippincott-Raven Publishers.