Physical and Chemical Properties of Thyrocalcitonin

Physical and Chemical Properties of Thyrocalcitonin 7.1. Purity and Potency 

While the purification procedures so far described undoubtedly achieve substantial increases in the specific activity of the material, until such time as products of consistent specific activity, homogeneous with re- 

Using intravenous infusions, Baghdiantz et al. (Bl) obtained a 10% fall in plasma calcium in the rat with relatively crude salt-fractionated pig thyroid extract containing 8 fig of protein nitrogen. The purest preparation reported by these workers appears to have been about 20 times more potent, i.e., 0.4 fig of protein nitrogen produced an approximately 10% fall. 

A standard preparation of thyrocalcitonin, prepared to the salt-fractionation stage by Method 2 above, is available from the Medical Research Council, Department of Biological Standards, National Institute for Medical Research, Mill Hill, London, and is distributed in ampules containing 0.25 MRC unit. When 0.01 MRC unit is injected intravenously into a 150-g rat, it produces a fall of approximately 10% in the plasma calcium after 50 minutes, i.e., this new unit is approximately 100 times larger than that described by Hirsch et al. (H4) and 1000 times larger than that of Baghdiantz et al. (Bl). From the in- 

Very little information is available regarding the amino acid composition of thyrocalcitonin. Tenenhouse et al. (T5) analyzed their most highly purified preparations, and calculated the following tentative empirical formula Lys 8, His, Arg 4, Thr 4, Ser 4, Glu 10, Pro 4, Gly 5, Ala 8, Val 4, Meth, Cys i/, lieu 3, Leu 9, Tyr 2, Phe 2, Try, and 

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