The Effect of Guanine Derivatives on Palmitate-1- 14 C Incorporation into Rat Epidydymal Adipose Tissue ∗

Summary

The incorporation of palmitate-1-¹⁴C into rat epidydymal adipose tissue lipids was markedly enhanced by the in vitro addition of guanosine and its 5′-phosphate esters and to a lesser extent by dGMP, G 2′, 3′cP, adenosine, uridine, and cytidine. Guanine and G3′(2′)MP were without effect. This stimulation of palmitate incorporation could not be duplicated by employing other known antilipolytic agents, such as nicotinic acid or PGE₁, and persisted under conditions where the specific activity of the incubating medium was kept constant, indicating that the stimulation obtained with guanosine and related compounds was not secondary to an inhibition of lipolysis in adipose tissue. The magnitude of the response to guanosine depended on the glucose concentration of the incubating medium and the nutritional state of the donor animal; little or no stimulation was obtained when esterification was already enhanced by the presence of glucose in the medium or when fat pads of fasted-refed rats were employed. Guanosine and its 5′-phosphate esters inhibited the oxidation of glucose-U-¹⁴C as well as its conversion to lipid by epidydymal adipose tissue.