| Popis: |
The platyfish, Xiphophorus maculatus , requires prolactin for survival in its natural fresh-water habitat but can be maintained in dilute sea water if deprived of the hormone. In the current study, males were transferred from fresh water to one-third sea water for periods ranging from 2 hr to 30 days, and several were returned from 30 days in the saline medium to fresh water for up to 72 hr. Progressive cytometric and cytological changes of the prolactin cells were compared with autoradiographic labeling after injections of tritiated leucine. Reduced synthetic activity, as judged by cytologic and autoradiographic evidence, was seen as early as 12 hr after the fish were placed into dilute sea water. A marked reduction in cytoplasmic granulation and cell size was first noted at 48 hr, suggesting that hormonal release was continuing independently of the rate of synthesis during this period. After 30 days, cytometry, cytology, and labeling of the prolactin cells were similar to that observed at 48 hr. There was cytologic and autoradiographic evidence of increased synthetic activity in the prolactin cells by 72 hr after the fish were returned to fresh water from 30 days in one-third sea water. Our observations suggest that there is a reduction in synthesis when platyfish are placed in sea water which can be increased when they are returned to fresh water. These changes in synthetic activity presumably reflect requirements for prolactin in these two environments. |
