PROLACTIN ACTION ON EXTRACELLULAR FLUID VOLUME IN TAILS OF STAGE-XII BULLFROG TADPOLES

The effect of prolactin (PRL) on electrolyte and water content of total tail and tail muscle tissues of stage XII bullfrog tadpoles was studied after injection of ovine PRL or removal of endogenous PRL by injection of a specific antiserum to ovine PRL (PRL A S). PRL treatment (5 μg per tadpole daily for 5 days) caused a significant increase in sodium and water content while potassium content of total tail tissues decreased, when compared to saline-treated controls. No differences were observed in electrolyte and water content in tail muscle tissues, and plasma electrolyte concentrations were unchanged. These data indicate that the increased tail sodium and water represent an expansion of extracellular fluid volume in the tail fin. Injection of PRL A S (every 5 days for 15 days) caused a decreased sodium and water content of total tail tissues as compared to control animals injected with normal rabbit serum. Again, no differences were found in tail muscle electrolytes, water content, and plasma electrolyte concentrations in the PRL A S group. Thus, removal of endogenous PRL caused a decreased extracellular fluid volume in the tail. These results indicate that a prolactin-like substance is present in stage XII bullfrog tadpoles and may be involved in chronic regulation of extracellular fluid volume in the tail fin. © 1979.