Effects of insulin on the fine structure of hepatocytes from winter-acclimatized carps: studies on protein synthesis.

Male and female winter-acclimatized carps were injected with insulin. This treatment resulted in a sharp decrease in the liver glycogen content. Although an increase in the ribosomal RNA level was also observed, a cell-free system obtained from the hormone-treated fish exhibited less amino acid incorporation activity as compared to the control fish. However, polysomes from insulin-treated fish exhibited a higher amino acid incorporating activity when a soluble fraction of untreated winter carps was used. Insulin induced a profound change in the cytoarchitecture of the winter carp hepatocyte. The cytoplasm and nuclei showed all the features of the summer carp liver cell. The nucleolar components were totally intermingled suggesting a high rate of gene expression as in the case of the summer-acclimatized fish.