Differential expression of gap junction connexins in endocrine and exocrine glands

We have investigated the expression of three gap junction proteins and their corresponding mRNAs by secretory cells of a variety of junctions of endocrine and exocrine glands. Byimmunostainin cryostat sections (indirect immunofluorscence) with antibodies against connexins (Cx) 26, 32, and 43 and by hybridizing total glandular RNA (Northern blot) with cRNAs for these proteins, we have found that several exocrine glands (lacrimal gland, salivary glands, pancreas, prostate, and seminal vesicle) express high levels of Cx32 and veriablelevels of Cx26, but no Cx43. Thus, different sets of proteins comprise the gap junctions of endocrine and exocrine glands.Together with the findings that an endocrine gland (thyroid) that discrages secretory products extra Together with the findings that an endocrine gland (thyroid) that discharges secretory products extracellularly before releasing them in the vascular compartment expresses both Cx43 and that an exocrine gland (preputial gland) that has a pheromonal role expressed Cx43, these observations sugest that the differential expression of gap junction connexins may be required to specify the endocrine or exocrine differentiation of a secretory cell.