Acute Inhibition of Thyroid Function in the Rat Produced by Rabbit Antibody to Beef Thyrotrophic Hormone. ∗ †

Abstract

Rabbit antibody produced in response to injection of bovine thyrotrophic hormone (TSH) effectively neutralizes the thyroid stimulating activity of injected rat pituitary extract(1). Since the anti-beef TSH antibody interferes with the effects of exogenous rat TSH, it seemed likely that the antibody could also inactivate circulating endogenous hormone in this animal. An analogous experiment, the production of acute diabetes mellitus in the rat has already been accomplished by Wright(2) using an anti-beef insulin antibody produced in the guinea pig. In the following experiment thyroid function has been measured continuously in the rat by the in vivo counting of neck radioactivity following injection of radioactive iodine; the effects of injection of antibody were then tested during the course of a thyroid I¹³¹ release curve. An abstract of this work has been published(1).

Methods. Antibody to bovine TSH was produced in rabbits by the method of Werner et al.(3). Adult male New Zealand rabbits were injected in multiple intracutaneous sites with an emulsion of Thytropar (Armour Laboratories) in Freund's adjuvant. Three series of injections of 3 units each were given at 10-day intervals. The initial injection was with the complete adjuvant; later injections used incomplete adjuvant. Plasma was harvested 10 days after the last injection and at intervals after booster injections of one unit and was stored in the frozen state. Thyroid I¹³¹ release curves were determined by serial neck counts of groups of adult male rats injected with 40 μc of radioiodine 24 hours prior to the initial neck count(4).

Results. (Fig. 1). Following a control period in which initial I¹³¹ release rates were determined one group of 6 rats was injected intraperitoneally once a day for 3 days with plasma from TSH-immunized rabbits.