DETERMINATION OF THYROTROPHIN BY MEANS OF RADIOACTIVE PHOSPHORUS

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Abstract
150 g. guinea pigs were kept at 30-32[degree]C for 12 days, then given one injn. of test substance per day for 2 days (vol. of injn. = 1 ml.); 24 hrs. later injd. with 0.05 [mu]curies P32 in 5% dextrose intraperit. 40 min. later animals were killed by a blow on head, thyroids weighed and left lobe fixed for histological examination (measurement of cell height); right lobes of 3 animals pooled for detn. of P and radioactivity with beta-ray Geiger counter. The P32 method measures a total dose of 2 to 16 guinea pig units. The slope of dose-response curve is steeper than for cell height, and, therefore, more accurate. Max. response of cell height = 100%; of P32 uptake = 1100% increase over controls.