EFFECTS OF 3-HYDROXYBUTYRATE ON THE HYPOXIC AND REOXYGENATED ATRIA FROM FED AND FASTED RATS

When exposed to hypoxia, the isolated atria from fed rats released lac tate into the medium and underwent a decline of the peak developed ten sion and pacemaker frequency. The atria from 24-h fasted rats showed a rise in the resting tension together with a greater decline of the pa cemaker rate and a lower lactate output than those from fed rats. The exposure to 5 mM 3-hydroxybutyrate caused only a small and brief decli ne in the pacemaker rate in the fed rats atria indicating that ketone bodies are able to exert only a minor detrimental effect on the hypoxi c atria. Since the lactate output remained unaffected, this effect can not be ascribed to a lowering in the energy supply from anaerobic glyc olysis. On the contrary, 3-hydroxybutyrate improved the post-hypoxic r ecovery of the peak tension in the atria from fasted ran. This finding may be reflecting an anaplerotic role of 3-hydroxybutyrate, thus sugg esting that in addition to glucose a second substrate is needed to mee t the energy demand in the reoxygenated atria from fasted rats.