Abstract
Rat serum TSH has been assayed using the discharge of unbound 131I– from guinea pig thyroid slices. Nonspecific responses occur with untreated rat serum. Filtration of serum on Sephadex G-25 removes the interfering factors, permitting the estimation of rat serum TSH levels with quantitative recovery. Mean normal serum levels were 6.5 and 4.7 International mU/100 ml (males and females, respectively, the difference being nonsignificant). Serum activity was reduced by antiserum to 0.18 mU/100 ml and by T4 treatment (75 μg daily for 5 days) to 0.25 mU/100 ml, these residual responses lying close to the end—point of the regression. Prior oophorectomy had no significant effect upon this serum activity of T4 treated rats. Propylthiouracil (0.1% in drinking water for 102 days) elevated the mean level to 93 mU/100 ml. Departures from parallelism with International Standard TSH occurred in 14 of 40 assays of normal rat serum. No departures were detected in 13 such assays against a rat pituitary fraction (potency 1....
Sign-in/Register to access full text options 
Free) 
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 call
