Evidence for Thyrocalcitonin Binding to Protein in Plasma

Abstract

SUMMARY A simple method is described for concentrating thyrocalcitonin from plasma by adsorption onto finely divided silica gel. An approximately 20-fold increase in biological activity with respect to protein content has been obtained with recoveries of added material of about 80%, allowing subsequent fractionation and bioassay of the fractions. Porcine thyrocalcitonin was added to either porcine or human plasma to give concentrations within the range observed in porcine thyroid venous plasma. Concentration on silica gel followed by gel filtration on Sephadex G 50 resulted in separation of the biological activity into two fractions, one of which was associated with the plasma proteins. A similar result was obtained with porcine thyroid venous plasma containing endogenous thyrocalcitonin. Preparative ultracentrifugation of plasma rich in thyrocalcitonin also provided evidence suggestive of some protein binding of the hormone. It is concluded that thyrocalcitonin is carried in plasma partly free and partly bound to plasma protein.

A Possible Role for the Adenyl Cyclase System in Calcitonin Release

“…The bioassay of calcitonin was based upon the measurement of the hypocalcaemic response of rats to the intravenous injection of solutions containing calcitonin (Leggate et al 1969). The index of precision in five consecutive assays was 0-14 to 0-21.…”

“…Calcitonin secretion was examined by two techniques : (a) Qualitative estimation of CT secretion was obtained by allowing the venous effluent of the isolated perfused gland to return to the animal. Under these conditions, relative changes in CT secretion could be inferred from alterations in the systemic concentration of plasma calcium, (b) Calcitonin secretion rates were estimated quantitatively by measurement of CT concentration in the thyroid venous effluent by bioassay (Leggate, Care & Frazer, 1969) or radioimmunoassay . The plasma flow rate through the gland was calculated from the haematocrit of the venous effluent and the volume of blood collected from the isolated gland in a known time.…”

The Effects of Hypermagnesaemia on Calcitonin Secretion in Vivo

“…Calcitonin concentration was measured either by bioassay in rats (Leggate, Care & Frazer, 1969) or by radioimmunoassay (Temler & Felber, 1969;Bell, 1970). In two experiments, similar changes in CT secretion rate were observed when plasma CT was measured by both bioassay and radioimmunoassay, so that valid comparison could later be made between the results of experiments in which one or the other of these methods had been used.…”

Calcitonin-Like Activity in the Circulation of Osteopetrotic Grey-Lethal Mice

“…Using the method of Leggate et al (1969), an experiment was performed to see if the hypocalcaemic activity of the grey-lethal mouse plasma remained after a three¬ fold concentration and partial purification. To assess activity the lyophilized samples a.a 'fi s…”

“…Plasma was concentrated and partially purified according to the method of Leggate, Care & Frazer (1969). Three millilitres of pooled grey-lethal mouse or normal control plasma was adsorbed on to 75 mg finely divided silica gel and after shaking the slurry for 10 min it was centrifuged and the supernatant removed.…”