Abstract
Experimental hypothyroidism was induced in rats by the administration of NaClO4. Hearts from normal and hypothyroid rats were homogenized, and the extracts were assayed for phosphofructokinase-1 and phosphofructokinase-2 activity and fructose 2,6-bisphosphate concentrations. Hypothyroidism was associated with a drastic loss of phosphofructokinase-1 activity. A hyperbolic relationship between plasma thyroxine concentrations and phosphofructokinase-1 activity was found. As treatment with NaClO4 progressed, the decrease in blood thyroxine was faster than the decrease in enzyme activity. After prolonged hypothyroidism (a decrease in thyroxine of more than 10-fold), a 4-fold decrease in phosphofructokinase-1 activity was observed. In this metabolic condition 2-fold decreases in phosphofructokinase-2 activity and in fructose 2,6-bisphosphate were observed. A similar decrease in phosphofructokinase-1 activity in a partially purified preparation was found. The addition of L-thyroxine in the diet had little effect on phosphofructokinase-1 activity. However, exposure of minced pieces of hearts of hypothyroid rats to tri-iodothyronine for 5 h resulted in a clear increase in phosphofructokinase-1 activity, which was partially prevented by the simultaneous addition of cycloheximide. These results could account for the decrease in carbohydrate metabolism in heart from hypothyroid rats.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
