Action of Insulin on the Isolated Rat Diaphragm in the Presence of Actinomycin D and Puromycin

Abstract

WITHIN recent years, conclusive evidence has been obtained of a direct stimulation of transport of sugar from the extracellular to the intracellular space of the isolated perfused heart of the rat¹ and the isolated ‘caged’ diaphragm of the rat². It is, however, difficult to explain the entire mechanism of insulin action through this effect, for clear-cut insulin-induced stimulations have been observed in the absence of extracellular or intracellular glucose: these effects include biosynthesis of proteins from labelled precursors³, increased labelling of RNA from ¹⁴C-adenine or glucose⁴ and increased specific labelling of high-energy phosphates from intracellular inorganic phosphate labelled with phosphorus-32 (ref. 5). This evidence raised the question⁴ whether an induced biosynthesis of messenger RNA (ref. 6), which could in turn stimulate the synthesis of specific enzymatic proteins, may participate in the hormonal action; recent work on the effects of other hormones^7,8 supports this hypothesis.