TABLE 1.

Affinity values, and percentage and subcellular location of binding sites for α₁-adrenoceptor drugs in submandibular gland acinar cells (SMG-C10).

A
Drug	Ki (nM)	nH	KiH (nM)	% High	KiL (nM)	% Low	n
Prazosin	0.33 ± 0.1	−0.75 ± 0.1					4
BMY 7378	122 ± 27	−0.87 ± 0.2					4
5-methylurapidila		−0.58 ± 0.1	0.64 ± 0.3	21 ± 4	91 ± 7	79 ± 5	5
B
% [3H]Prazosin Binding				19 ± 2		71 ± 3
Sucrose Density Gradient Fraction Number				3 – 5b		9 – 10c

A. The values are mean ± S.E.M.; n, number of separate SMG-C10 cell cultures. K_i, is affinity in nM of drugs for inhibiting specific [¹²⁵I]HEAT binding; n_H, Hill coefficient. Affinity values from binding data that fit best to a two-site binding model are expressed as K_iH (high-affinity binding site) and K_iL (low-affinity binding site). % High, percentage of high-affinity binding sites; % Low, percentage of low affinity binding sites. B. % [³H]Prazosin Binding, percentage of specific [³H]prazosin binding sites in subcellular fractions separated by sucrose density gradient centrifugation. Values are mean ± S.E.M. of five experiments using separate SMG-C10 cell cultures.

^aCompetition binding curves fit best by nonlinear least-squares curve-fitting regression to a two-site binding model (p < 0.05) using the F test.

^bFractions containing intracellular vesicles.

^cFractions containing plasma membranes.