Loretta Van Camp

When a solution containing the complex ion, [PtCl6]=, and NH4+ ions is irradiated, a photochemical change occurs in which the chloride ions of the ligand are sequentially replaced by 1, 2, or 3 ammonia molecules. The total charge on the complex ion decreases by 1 negative charge for each replacement. These changes can be followed by changes occurring in absorption spectra or in ionophoretic patterns. Each charged species of the complex has a unique effect on the bacteriological growth of Escherichia coli. The doubly negative species is a bacteriocide. The singly negative species appears to have little effect on either growth or cell division processes. The neutral species has little effect on growth, but markedly inhibits cell division processes, forcing filamentous growth. The cis and trans forms of the diamino complex, [PtCl4(NH3)2]0, have been synthesized. The absorption spectra of both have a λmax at 207 mµ. The electrophoretic patterns indicate predominantly neutral species in both cases. The trans form is relatively inefficient in inhibiting cell division, whereas the cis form is fully as efficient as the neutral species in inhibiting cell division. We identify the neutral species as the cis form of the complex.

INTRODUCTION: Gap junctional intercellular communication has been implicated in the homeostatic regulation of cell growth, differentiation, and apoptosis. Cancer cells, which have been viewed as "partially blocked stem cells," and which lack the ability for growth control, terminal differentiation, and apoptosis, also lack functional gap junctional communication. AIMS AND METHODOLOGY: A clone of a human pancreatic ductal epithelial cell line, H6c7, derived after immortalization with human papilloma virus, was used to examine gap junctional intercellular communication and the ability to differentiate under different growth conditions. RESULTS: The cells showed characteristic epithelial morphology on standard tissue culture dishes. When placed on Matrigel they showed phenotypical changes with extensive ductal organization and budding structures. In growth medium containing hormones and growth factors, these cells were gap junctional intercellular communication (GJIC)-incompetent. In the presence of c-AMP elevating agents, isobutylmethylxanthine, and forskolin, in basal medium that did not contain the hormones and growth factors, the cells became GJIC-competent and expressed connexin43 gap junction protein within 48 hours after treatment. RT-PCR analyses of the cells under different growth conditions showed that the cells expressed, and genes when cultured in the basal medium with c-AMP elevating agents. They also expressed the gene that did not change with c-AMP treatment. H6c7 cells also have the capacity to turn on an ectopic insulin promoter reporter gene. CONCLUSION: Our data suggest that the immortalized H6c7 cells retain stem-like characteristics and have the potential to differentiate into duct-like structures and perhaps insulin-producing cells.