Cardiac Hypertrophy in Spontaneously Hypertensive Rats

Abstract

The energy metabolism of cardiac hypertrophy in spontaneously hypertensive rats (SHR) was studied chronologically by histochemical and in part chemical methods. The activities of various enzymes, such as glucose-6-phosphate dehydrogenase (G6PDH), lactate dehydrogenase (LDH), isocitrate dehydrogenase, succinate dehydrogenase, Β-hydroxy-butylate dehydrogenase (Β-HBDH) and monoamine oxidase (MAO) in the cardiac muscle were determined histochemically. Β-HBDH activity was greatly increased in the stage of developing hypertension in SHR. LDH activity increased simultaneously with the rise of Β-HBDH activity. Moreover, MAO activity increased markedly in later stages when the blood pressure was already elevated in SHR. To confirm the histochemical findings of Β-HBDH activity, the mitochondrial fraction of cardiac muscle was subjected to chemical assay. The chemical findings of myo-cardial Β-HBDH in SHR corresponded well with the histochemical findings. The myocardial Β-HBDH activity in SHR increased markedly at the age of 5 to 9 weeks, while no or minimal activity was found in controls of the same age. No significant difference of Β-HBDH activity was observed between SHR and controls in the mitochondrial fraction from the diaphragm and liver. The increase of Β-HBDH activity in the cardiac muscle of SHR prior to the development of cardiac hypertrophy suggests that the metabolism of ketone bodies may play an important role in providing the energy necessary for the development of cardiac hypertrophy in SHR.