Recent work in our laboratory indicated that the liver of rats and pigeons secretes a prolactin synergist (synlactin) in vitro. We have investigated the secretion of this activity by the liver of nine species of ectothermic vertebrates. Liver from three teleosts (goby, salmon, and tilapia), four amphibians (Ambystoma, Necturus, bullfrog, and grass frog) and two reptiles (turtle and anole) was diced, washed, and incubated for 3 hr in isotonic medium. After dialysis, the liver incubation media (LIM) were tested with and without prolactin (PRL) in the local pigeon crop-sac bioassay. The LIM for turtle, larval bullfrog, freshwater salmon, and 5% seawater-adapted goby significantly augmented the local crop-sac response to PRL, but the LIM from anole, adult bullfrog, grass frog, fasted larval Ambystoma, Necturus, 100% seawater-adapted goby, and tilapia did not contain synergizing activity. We conclude that synlactin is secreted by the liver of several species representing three of the major ectothermic classes of vertebrates. It is significant that in two cases, larval bullfrog and 5% seawater-adapted goby, the presence of synlactin occurs in physiological states in which PRL is active. In the opposite cases (adult frog and 100% seawater-adapted goby) the activity was not detectable. We also found that the liver of larval and adult bullfrogs and tilapia released a factor in vitro that had proliferative activity in the crop-sac. This activity appears to be distinct from synlactin.
Amphibians Animals