The role of prostaglandins in the control of protein turnover in tissues of the rat and the rainbow trout (Salmo Gairdneri, Richardson)
The possible role of the prostaglandins (PGs) in the regulation of protein turnover was investigated, firstly in hypertrophying rat skeletal muscle at 20 hours, 3 days and 7 days after synergist tenotomy, and secondly, in various tissues of the rainbow trout (Salmo gairdneri, Richardson) following re-feeding. An inhibitor of PG synthesis was used in both cases (fenbufen and indomethacin, respectively). 1) Fenbufen (at a dose of 1200mg/kg of diet) did not inhibit the hypertrophy of the soleus and plantaris muscles although there appeared to be an initial reduction in muscle RNA content. 2) Muscle growth was generally increased in fenbufen fed rats by 7 days after synergist tenotomy (10 days on fenbufen diet). 3) The fractional rate of protein synthesis in both control and overloaded muscles was reduced by fenbufen at this time (in 86g rats). The calculated rates of protein breakdown were also reduced in these muscles but to a greater extent than synthesis. This inhibition of protein degradation was most marked in the overloaded soleus and plantaris muscles. 4) The tenotomised gastrocnemius muscle experienced a true atrophy in the fenbufen-treated rats by 7 days. This atrophy involved greatly elevated rates of protein degradation when compared to the tenotomised muscle from rats fed a normal diet. In 6 day fasted rainbow trout, tissue protein synthesis was measured at 3 hours, 6 hours and 12 hours after re-feeding. The rapidity of the stimulation of protein synthesis by re-feeding and the nature of the response was tissue-specific. The administration of indomethacin (at a dose of 2mg/100g body weight) one hour prior to the meal, partially blocked the re-feeding response of protein synthesis in the gill at 6 hours after the meal, but stimulated protein synthesis in the liver and white muscle at this time.