Regression, proliferation and development of lip papillomas in wild white suckers,Catostomus commersoni, held in the laboratory

Synopsis

Epizootics of skin neoplasms in teleost species have been documented within the Great Lakes region over the last decade. The white sucker,Catostomus commersoni, has been proposed as a sentinel species to monitor environmental health in these systems. The prevalence of skin neoplasia is elevated in white suckers and other fish taken from chemically polluted sites or from lake regions adjacent to heavy industry. Lip papillomas regress and proliferate spontaneously in captive wild suckers. It is important to investigate the relevance of these observations to papilloma etiology to determine whether the prevalence of this disease is a suitable biomarker for environmental health. White suckers were captured in the spring of 1992 and 1993 during annual spawning runs (mid to late April) at the Ganaraska River, which discharges into Lake Ontario at Port Hope, Ontario. Under crowded laboratory conditions, there was either proliferation of existing papillomas or development of new papillomas. However, in uncrowded conditions, existing papillomas either regressed completely or there was no development of new papillomas. Protein Kinase C (PKC), a proposed marker enzyme for hyperplasia and neoplasia, was used to determine if regressing and proliferating papillomas could be differentiated on the basis of biochemical activity. PKC activity was lower in proliferating papillomas, but not significantly different from papillomas sampled initially from Ganaraska River suckers. Regressing papillomatous tissue displayed a significantly higher level of enzyme activity than either proliferating or unchanged papillomas, but the PKC activity of regressing papillomas was not significantly different from that of normal lip epidermis.