FACTORS REGULATING THE PRODUCTION OF VASOPRESSIN-ASSOCIATED HUMAN NEUROPHYSIN BY SMALL-CELL CARCINOMA OF THE LUNG - EVALUATION BY COMPUTER-ENHANCED QUANTITATIVE IMMUNOCYTOCHEMISTRY

Expression of the vasopressin gene appears to be a property common to all small-cell lung tumours. For some cultures of small-cell lung carc inoma (SCCL), Northern and Western Blot analyses have revealed that ex pression of this gene and its protein products are regulated by cAMP a nd glucocorticoids. In this study, these evaluations have been extende d by examining the production of vasopressin-associated human neurophy sin (VP-HNP) by computer-enhanced quantitative immunocytochemistry in a classical cell-line (H69) of SCCL, and defining the amount of protei n in cells by area of positive staining above an arbitrarily set thres hold. Intracellular cAMP was raised by incubating cells with either 8, Br-cAMP (0.5 mM) and IBMX (0.5 mM), or with forskolin (25 mu M) and IB MX (0.5 mM). Both of these treatments caused a significant increase in the amount of positive VP-HNP immunoreactivity in the cells, an incre ase that was further enhanced by simultaneous administration of dexame thasone (0.1 mu M). Addition of dexamethasone alone, however, caused a significant decrease in VP-HNP levels. Results confirm earlier findin gs from Western Blot analysis revealing the influence these agents hav e on production of vasopressin gene-related proteins by H69 cells, and indicate that computer-enhanced quantitative immunocytochemistry can be effectively used to provide a suitable index of this production.