Low particulate type IV phosphodiesterase activity in hypothyroid rat atria.
Rats were made hypothyroid by adding propylthiouracil (PTU) to their drinking water. Some of the PTU-treated rats were given thyroid hormone injections for 5 days. Both soluble and particulate cAMP-phosphodiesterase activities of adipose and ventricular tissues were increased by 25-60% in hypothyroidism. In left atria, soluble cAMP-phosphodiesterase activity was not significantly altered in hypothyroidism, while total particulate cAMP-phosphodiesterase activity was lowered by 30%. This lowering was due to diminished isoenzyme IV activity, as studied with the isoenzyme-specific inhibitors rolipram and SK&F 94836. In conclusion, the present results show decreased particulate type IV cAMP-phosphodiesterase activity in hypothyroid rat atria. This may explain the increased responsiveness to isoproterenol in hypothyroid atria.
Kaasik
A
A
Department of Medical Chemistry, University of Helsinki, Finland.
Elomaa
V V
VV
Seppet
E K
EK
Ohisalo
J J
JJ
D000818:Animals; D006325:Heart Atria / Q000201:enzymology*; D006352:Heart Ventricles / Q000201:enzymology*; D007037:Hypothyroidism / Q000201:enzymology*; D007527:Isoenzymes / Q000378:metabolism*; D010316:Particle Size; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D007527:Isoenzymes; D010727:Phosphoric Diester Hydrolases