Beta-adrenergic receptor in heart of starved rats

Female Wistar-strain rats were starved for 14-19 days by feeding approximately 1/4 of the amount consumed by ad libitum fed controls. The body weight was reduced by 41% and the heart weight by 38% in these starving periods. The 125I-iodocyanopindrol (ICYP) binding capacity of heart preparations from the starved rats was 35.3 +/- 11.1 (mean +/- SD) fmol/mg protein in comparison with 69.3 +/- 14.9 for the controls. Serum 3,5,3'-triiodothyronine (T3), thyroxine and TSH levels as well as pituitary TSH contents were markedly lower in the starved rats. One group of them further received 20 ng of T3 daily after the 8th day of the experiment. The body weight decreased by 47% of the controls but the ICYP binding capacity recovered to 56.3 +/- 10.9 fmol/mg protein. There was no difference in association constants of the receptors in these three groups. It was concluded that quasi-chronic starvation in rats caused a remarkable decrease in the number of beta-adrenergic receptors in heart and this was partly offset by the substitution of T3.