Rat TSH: Radioimmunological verification and secretion in vitro

The rat TSH radioimmunoassay with 125I was worked up and validated. Measurement area: 300-104 ng TSH/ml, lower detection limit 200 ng/ml, intra-assay variance 3-5%, inter-assay variance 11-18%. For the study of TSH secretion in dispersed anterior pituitary cells, these cells were subjected to an one-hour incubation with a changing TRH concentration. This system, however, did not prove to be sensitive enough for a TRH-in vitro-bioassay. A culture of vital, functioning cells in micro-titer plates up to 30 days was possible. After stimulation with 10-11 to 10-6 M TRH over 2 hours a linear dose-dependent increased secretion of TSH with a maximum TSH response of 300% was shown. After fractionation of the anterior pituitary cells after a sedimentation over an albumin gradient it was shown that after fraction 40 there was an increase in the TSH content with a massive increase in TSH cells around fraction 60. The TSH content lay here around the factor 200 above that of the original suspension. A culture of pure TSH cells is therefore possible and for further studies accessible. (orig.)