THE ALPHA-2-ADRENOCEPTORS OF THE HUMAN RETINOBLASTOMA CELL-LINE (Y79) MAY REPRESENT AN ADDITIONAL EXAMPLE OF THE ALPHA-2C-ADRENOCEPTOR

1 In agreement with the literature, correlation of the ability of a series of agonists and antagonists to displace [H-3]-rauwolscine binding shows the alpha-2-adrenoceptors of HT29 cells, NG108-15 cells, OK cells and homogenates of rat sublingual gland to represent four distinct subtypes. 2 [H-3]-rauwolscine also bound with high affinity (K(D)=0.30 +/- 0.10 mM) to a human retinoblastoma cell line (Y79). Specific binding represents 73% of total binding, and a B(max) of 38 +/- 1 fmol mg-1 protein was determined. 3 Correlation of antagonist affinities against [H-3]-rauwolscine with corresponding values in the other four tissue sources showed the Y79 cells to resemble most closely the OK cells, the prototype example of an alpha-2C-adrenoceptor, with a correlation coefficient of 0.90 and a regression slope of 1.01 being obtained for 10 antagonists in these two systems. 4 Comparison of K(D) values for [H-3]-rauwolscine also showed a similarity between the OK cells (0.19 +/- 0.07 nm) and Y79 cells. 5 These data suggest that the human retinoblastoma cell line may represent an additional example of the alpha-2C-adrenoceptor subtype.