LOCALIZATION OF THE G-PROTEIN G(0) IN EXOCRINE GLANDS

The GTP-binding protein G(o) was localized immunohistochemically in th e rat parotid gland and in other exocrine glands with specific G(o) an tibodies. Immunohistochemical studies revealed that affinity-purified G(o alpha) polyclonal antibody (GO/85) immunoreacted primarily with du ct cells of the rat parotid gland; immunoreactivity was also noted in duct cells of the rat submandibular, mouse parotid, and mouse submandi bular glands. Light labeling of rat parotid and submandibular gland ac inar cells was also noted. G(o alpha) antiserum (9072) differing in sp ecificity for epitopes within G(o alpha) produced similar results. Thi s antiserum also immunoreacted with rat submandibular duct cell secret ory granule membranes. In contrast, in rat and mouse pancreas G(o alph a) antibodies immunoreacted primarily with islet cells. Duct cells wer e negative but there was light labeling of rat pancreatic acinar cells . The apparent duct specificity of G(o alpha) staining was further ver ified by demonstrating that G(o alpha) antibodies immunoreacted with H SG-PA cells, a human transformed salivary duct cell line. Specificity in immunohistochemical labeling of HSG-PA cells was confirmed by Weste rn blot analysis. The results demonstrate that G(o) appears to be sele ctively expressed in the duct cells of rat parotid gland and other sal ivary glands. The selective enrichment of G(o) in duct cells suggests that this G-protein plays an important role in duct cell physiology.