THE PRESENCE OF SIGMA-RECEPTORS IN THE LACRIMAL GLAND

Applying the technic of S.A. Wolfe et al. [Endocrinology, 124, 1160-11 72, 1989], we have established the presence of sigma receptors in isol ated, but intact, lacrimocytes excised from main lacrimal gland tissue of the New Zealand white rabbit. H-3-Haloperidol was used as the liga nd (0.5-2500 nM), in the presence of spiperone. From a Scatchard plot, a single binding site was statistically chosen over two sites for a m ajority of the data associated with the intact lacrimocytes. K(d) (71. 0 +/- 46.4 nM) and B(max) (588.2 +/- 166.7 fmol/mg of protein) values showed lower binding affinity but a similar density of sigma sites in rabbit lacrimocytes when compared to published results obtained for ra t exocrine glands and brain tissue. Using the technic of McCann and Su [J. Pharm. Exp. Therap., 257, 547, 1991], membrane suspensions of the sigma receptor were also prepared and tested for binding to radioliga nds, H-3-DTG, as well as H-3-haloperidol. A Scatchard plot revealed tw o binding sites for H-3-DTG and one binding,site for H-3-haloperidol. The high affinity site for H-3-DTG yielded a K(d) of 1.04 +/- 0.64 nM, whereas, B(max) was 135.9 +/- 11.62 fmol/mg of protein. The low affin ity site gave a K(d) = 75.3 +/- 26.8 nM and B(max) = 344.0 +/- 222.0 f mol/mg of protein. The weaker site is suspected to be intracellular. I C50 values were determined for N,N-disubstituted arylphenylalkylamines (Kd almost-equal-to low nM).