The effect of triiodothyronine on myocardial protein kinases.

Rats treated with T3 (triiodothyronine) showed an increased heart weight after 3 days reaching 100% after 3 weeks of treatment compared to untreated controls. Cytosol protein kinases were not significantly different in the T3 treated rats compared to controls. The protein kinase activity of the NHP (nonhistone proteins) increased after 2 hours and doubled after 3 days for each substrate tested. After 1 week of T3 treatment the protein kinase activity returned to the control value and remained at the control level for the remainder of the 3 week experimental period. A study of the distribution of protein kinase activity in the NHP by disc gel electrophoresis showed that there was a difference in the distribution of some peaks in the T3 treated animals compared to the controls. T3 in concentrations from 10(-11) to 10(-3) M had no in vitro effect on the phosvitin kinase activity of NHP and of cytosol.