Autoradiographic quantification of adrenergic receptors in rat kidney.

The adrenergic nervous system is active in kidney function, and the kidney has large numbers of adrenergic receptor subtypes. Because of the cellular complexity of the kidney, it is difficult to obtain direct assessments of adrenergic receptor binding characteristics over specific tissue compartments. Qualitative autoradiography allows the localization of adrenergic receptors over tissue types in the kidney, but quantitative autoradiography allows direct comparison of adrenergic receptor number over different cellular compartments. The purpose of this study was to obtain direct assessments of alpha 1, alpha 2, and beta adrenergic receptor numbers over different tissue compartments of the kidney using quantitative autoradiography. Sections of Sprague-Dawley rat kidney were incubated in several concentrations of 3H-dihydroalprenolol to label beta receptors, 3H-prazosin to label alpha 1 receptors and 3H-rauwolscine to label the alpha 2 receptors. Sections of rat heart incubated in 3H-dihydroalprenolol were included as standards. The sections were then prepared for receptor autoradiography. After processing, the grains were then quantified on an image analysis system, and binding curves constructed from the specific binding. In some animals, the proximal tubules were stained to localize the proximal convoluted tubules. Significant Scatchard analyses were obtained in the glomeruli with dihydroalprenolol (5.18 X 10(9) receptors/mm3) and with rauwolscine (2.48 X 10(9) receptors/mm3). Significant Scatchard analyses were obtained in the cortex with rauwolscine (9.47 X 10(9) receptors/mm3) and with prazosin (3.9 X 10(9)). In addition, specific binding was seen with rauwolscine and prazosin to the kidney arterioles.(ABSTRACT TRUNCATED AT 250 WORDS)