The effects of cortisol treatment on carbohydrate and protein metabolism in Fundulus heteroclitus

Abstract

In male Fundulus heteroclitus captured during the fall, 5 daily injections of cortisol (200 μg/fish or approximately 20 μg/g body wt) produced significant elevations in serum cortisol and hyperglycemia in both fed and fasted fish. Only fasted fish responded with an increase in liver glycogen. No consistent changes attributable to hormone injection occurred in serum protein, amino acid, liver protein, liver amino acids, or liver alanine aminotrasferase. A single cortisol injection (20 μg/g body wt) in fasted fish produced elevated blood glucose levels which persisted for 48 hr and followed serum cortisol changes closely. Again, no significant changes were seen in liver glycogen or in protein metabolism. We conclude that in F. heteroclitus, blood glucose is the major carbohydrate reservoir influenced by cortisol elevation. Protein catabolism appears not to be the source of the glucose elevation. Reduced peripheral glucose utilization and gluconeogenesis from lactate or glycerol are suggested as alternative sources.