Retinoic acid hydroxylation and teratogenesis in lake sturgeon (Acipenser fulvescens) from the St. Lawrence River and Abitibi region, Quebec

All-trans-retinoic acid (RA) is an extremely active form of vitamin A; howe ver, excessive or insufficient concentrations elicit anomalies including th ose associated with limb and craniofacial development. Lake sturgeon (Acipe nser fulvescens) from the St. Lawrence River and tributaries were estimated to have a 2.9% incidence of fin and craniofacial malformations. Among larv ae raised in artificial streams, a greater incidence of fin malformations ( 6.3%; p < 0.001) occurred in St. Lawrence River sturgeon compared with larv ae from the Abitibi region. To test the hypothesis that the differences in rate of malformations may be associated with metabolic imbalances of RA, cy tochrome P-450 dependent conversion to 4-hydroxyretinoic acid (COH-RA) was investigated. Optimal assay conditions are described for in vitro 4-OH-RA p roduction in liver microsomes. Enzyme activity tended to-decrease with incr easing age and gonadal development in fish collected from Abitibi, but no s tatistically significant effects of sex, age, length, or gonadal developmen t were discerned. The rate of 4-OH-RA formation was 3.5-fold greater (p < 0 .0001) in the St. Lawrence sturgeon while the concentrations of cytochrome P-450 inducing PCBs (expressed as dioxin toxic equivalents) were 20-fold gr eater in a composite liver sample of the St. Lawrence sturgeon. Liver retin oid concentrations were negatively correlated (p < 0.0001) with RA hydroxyl ation rate. These results are consistent with the possibility that cytochro me P-450 dependent RA metabolism increased by chemical contaminants is asso ciated with developmental anomalies in the St. Lawrence sturgeon.