The Effect of Refeeding on Tissue Protein Synthesis in Rainbow Trout

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Abstract
The fractional rate of protein synthesis ($K_{s}$ %/day-i.e., the percentage of tissue protein synthesized per day) was measured in various tissues of 6-day fasted rainbow trout at 3, 6, and 12 h after being refed. There was a significant stimulation in the rate of protein synthesis in all of the tissues except the white muscle by 3 h after refeeding. The red muscle, white muscle, and ventricle exhibited a slow, graded response, with the white muscle not reaching levels found in continually fed fish 12 h after the meal. The gill, stomach, and intestine showed a rapid rise in protein synthesis reaching a plateau after approximately 3 h. The liver exhibited a peak in protein synthesis within 3 h that subsequently declined. Generally, there was no effect of refeeding on tissue RNA/protein ratio (used to indicate tissue ribosome concentration) so that these changes in tissue protein synthesis were brought about through an increase in protein synthesis per unit RNA (which is indicative of an alteration in the rate of ribosomal translation). Following the injection of the prostaglandin synthesis inhibitor, indomethacin, only in the gill was the refeeding stimulation partially blocked, implicating the prostaglandins in the regulation of protein synthesis in this tissue.