Rates of protein synthesis by hepatocytes isolated from rats of various ages

Abstract

The rate of total protein synthesis in isolated hepatocytes was determined. The incorporation of L-[3H]valine into protein is linear for at least two hours of incubation and is affected by the concentration of amino acids in the medium. Uptake of valine by hepatocytes from 1.5- and 18-month-old rats was identical and appears to occur by simple passive diffusion. Within five minutes, the specific activities of the intracellular and extracellular valine pools are equivalent. The specific activities of these pools are saturated by 1.6mM valine and remain constant for 60 minutes of incubation. The rates of protein synthesis by hepatocytes from 1- to 2-month-old rats is 96.8 pmoles of valine per minute per milligram protein. This is comparable to rates of protein synthesis reported for perfused liver and liver in vivo and is approximately 64% higher than the rate of protein synthesis by hepatocytes from 18-month-old rats.

Age-associated changes in activities of rat hepatocytes. I. Protein synthesis

“…Our experiments corroborate previous reports of a diminished capacity of hepatocytes from aging rats to synthesize total protein [8,12]. This decline is most pronounced in aged animals and is manifest in depressed specific activities of incorporation in all subcellular fractions; depressions range from 60% for mitochondria to greater than 80% for the microsomal fractions ( Table 2).…”

“…It should be noted, however, that our experiments do not reveal a difference in incorporative activity of hepatocytes from immature as opposed to mature animalls. This result is in direct contrast to the reports of Ricca et al [8] and Van Bezooijen [12]. This discrepancy in findings may have at least two possible explanations: 1) our incubations were conducted with less than saturating levels of leucine so as to preclude a need for overlarge amounts of radioiscltope in the large scale experiments; 2) there may be hormonal or other strain differences between the animals of Zivic-Miller origin and those employed by previous investigators.…”

Influence of the Hepatic Eukaryotic Initiation Factor 2α (eIF2α) Endoplasmic Reticulum (ER) Stress Response Pathway on Insulin-mediated ER Stress and Hepatic and Peripheral Glucose Metabolism

“…ectopic fat accumulation and glucose homeostasis (5–9, 11). The liver maintains one of the highest protein synthesis rates in the body, with the majority of these peptides being processed by the ER (10), and it would therefore be expected to be prone to the metabolic changes induced by ER stress. However, the details of the relationship between ER stress and hepatic glucose and lipid metabolism and the causal links between them remain poorly understood.…”

Efeitos do deidroepiandrosterona (DHEA) sobre a função vascular e a resistência periférica à insulina em um modelo experimental de menopausa.

“…Ao final do tratamento foi realizada a medida direta da pressão arterial (PA) com animais acordados. Além disso, anéis de aorta foram isolados para avaliar resposta contrátil à fenilefrina (PHE, M) e a resposta de relaxamento à acetilcolina (ACh,(10)(11) M) e ao nitroprussiato de sódio (NPS,(10)(11). A resposta à PHE e à ACh também foi estudada em anéis incubados previamente com L-NAME (inibidor da NOS, 10 -4 M), superóxido dismutase (SOD, 150 U/mL), apocinina (inibidor da NADPH-oxidase, 10 -4 M) ou salicilato (inibidor do NFκB, 5 x 10 -3 M).…”

“…ectopic fat accumulation and glucose homeostasis (5)(6)(7)(8)(9)11). The liver maintains one of the highest protein synthesis rates in the body, with the majority of these peptides being processed by the ER (10), and it would therefore be expected to be prone to the metabolic changes induced by ER stress. However, the details of the relationship between ER stress and hepatic glucose and lipid metabolism and the causal links between them remain poorly understood.…”