Regional variation and differential sensitivity of rat heart protein synthesis in vivo and in vitro

Abstract

In vivo, fractional rates of protein synthesis in atrial muscle of hearts taken from fed rats were 70% greater than in ventricular muscle. After 3 days starvation, atrial protein synthesis is inhibited, but the inhibition is less than in ventricles. A crude subcellular fractionation of the aqueous homogenates by centrifugation at 32000g showed that the supernatant and precipitate proteins were synthesized at the same rate in the ventricles. The fractional rates of protein synthesis and RNA/protein ratios in the right ventricle were 10% greater than in the left ventricle. Protein synthesis in both of these regions was inhibited equally by starvation. In vitro, rates of protein synthesis in atria and ventricles of anterogradely perfused rat hearts were stimulated by saturating insulin concentrations and were inhibited by starvation, but the effects in atria were smaller than in ventricles. Rates of protein synthesis in atria in vitro were 80-95% of rates in vivo. The heart therefore shows considerable regional variation in rates of protein synthesis in vivo and in vitro, and the sensitivity of protein synthesis in the various regions to interventions such as insulin and starvation differs.

Protein Turnover in Ectotherms and Its Relationships to Energetics

“…13). Results from crude subcellular fractionation of rat ventricle have also pointed to similar fractional rates of protein synthesis in different fractions (Preedy et al 1985). When absolute rates of protein synthesis are calculated, the myofibrillar fraction turns out to be the major site of protein synthesis.…”

Phenylalanine Metabolism in Sheep Infused With Glucose Plus Insulin. Ii. Effects on in Vivo and in Vitro Protein Synthesis and Related Energy Expenditures

“…In contrast, insulin added to isolated muscle preparations from rats and rabbits generally increases FSR (Fulks et aL 1975: Jefferson et al 1977Palmer et al 1985). Preedy and Garlick 1983) and heart (11-20% d-t1, Preedy et al 1984Preedy et al , 1985 were similar to or lower than in vitro values. However, in vivo FSR in soleus (20% d-t; Goldspink et al 1983) and diaphragm 05% a-t' Preedy et al 1986) muscle from fed rats, Were twice as high as FSR in the isolated tissue.…”

“…Preedy and Garlick 1983) and heart (11-20% d-t1, Preedy et al 1984Preedy et al , 1985 were similar to or lower than in vitro values. However, in vivo FSR in soleus (20% d-t; Goldspink et al 1983) and diaphragm 05% a-t' Preedy et al 1986) muscle from fed rats, Were twice as high as FSR in the isolated tissue. In isolated forearm muscles from fed rabbits (Palmer et al 1981(Palmer et al , 1985 al.…”

“…In vivo FSR based on ICF SRA in muscle were not significantly different between G*I and S infused sheep Such comparisons are important since a number of studies in rats (Goldspink et al 1983;Preedy et al 1986) and rabbits (Palmer et al 1981;Palmer et al 1985) This experiment is reported in two parts.…”

Alcohol‐Induced Reductions in Cardiac Protein Synthesis In Vivo Are Not Ameliorated by Treatment With the Dihydropyridine Calcium Channel Blocker Amlodipine

“…However, experimental manipulation of the animal before removal of the heart for in vitro study may influence cardiac tissue per se. For example, we previously showed that cardiac protein synthesis is altered in vivo by anesthesia (Siddiq et al, 1991), surgical stress (Preedy et al, 1988), starvation (Preedy et al, 1988), and the in vivo to in vitro transition (Preedy et al, 1985). A good example of our supposition that examining alcohol toxicity in vitro has only limited relevance to the intact animal is derived from the studies described by Schreiber and colleagues, who showed that in the perfused heart, alcohol at a concentration of approximately 54 mmol/liter failed to reduce cardiac protein synthesis, whereas a dose of 325 mmol/liter reduced protein synthesis in their preparations (Rothschild et al, 1975a,b;Schreiber et al, 1972).…”