Physiological responses of larval and postmetamorphic Rana pipiens to growth hormone and prolactin

Abstract

AbstractBovine prolactin stimulates growth of tadpoles, whereas bovine growth hormone stimulates growth of postmetamorphic frogs. The biochemical composition of liver, muscle, and fat body were examined to determine whether there were any changes in carbohydrate, protein, fat, or nucleic acids which might correlate significantly with the growth effects of the hormones in the two stages of development. In the frog, the major effect of growth hormone was to depress carbohydrate and lipid stores, with little or no effect on protein and nucleic acids in most experiments. Prolactin had similar but smaller effects on carbohydrate, and no effect on fat body lipid in the frog. In tadpoles prolactin suppressed muscle glycogen, but otherwise did not affect tissue composition. Growth hormone had no effects in the tadpole. Ways in which the interrelated developmental and metabolic effects of growth hormone and prolactin could increase the adaptive significance of distinct larval and postmetamorphic growth‐regulating hormones in the amphibians are discussed.