ACTH EFFECT OF PITUITARY GLANDS OF PACIFIC SALMON DEMONSTRATED IN THE HYPOPHYSECTOMIZED COUESIUS PLUMBEUS

Abstract

This report deals with the cytology of the interrenal and chromaffin tissue in a small freshwater cyprinid, Couesius plumbeus. As in most teleosts, in this species, too, the two components were found to be intimately associated. After removal of the pituitary, the interrenal cells showed atrophy which could be reversed by injection of pituitary extracts of Pacific salmon (Oncorhynchus tshawytscha and O. kisutch). This extract was injected intraperitoneally in a series of six doses of 0.1 ml every second day, beginning 4–6 weeks after hypophysectomy. The fish were autopsied 2 days after the last injection. Mammalian ACTH, similarly injected in six doses of 0.25 or 0.50 international units per gram weight, exerted only a doubtful effect. In view of the transitory nature of the ACTH effect in similar experiments as reported in the literature, it is suggested that the time lapse between the last injection and the time of autopsy may have been too long to detect such an effect in our fish. The chromaffin cells did not react to any of the treatments in this investigation.