The influence of preliminary soaking on glucose utilization by diaphragm.

The isolated rat diaphragm has been used widely as a convenient tissue with which to study glucose utilization by muscle. Some data have been published on the influence of various extrinsic, non-hormonal factors on carbohydrate utilization by the diaphragm, such as substrate concentration, pH, and ionic environment (14). The principal effect to be discussed in this paper is the increase in glucose uptake which may be observed after various soaking procedures. As much as a 2-fold rise may occur as a result of soaking the diaphragm at a low temperature for a period of a few minutes prior to incubation. In our experience, this effect has not qualitatively altered certain well established hormonal influences but can obscure them if it is not appreciated. The time curves of glucose uptake and glycogen synthesis have also been studied and their relationship to the soaking phenomenon is discussed. In addition, a few observations are reported on the dependence of glucose uptake on the rate at which the diaphragm is shaken.