Establishment of a calcitonin-producing rat medullary thyroid carcinoma cell line. II. Secretory studies of the tumor and cells in culture.

Abstract

In the preceding paper we described the establishment of a calcitonin(CT)-producing cell line from the WAG/Rij transplantable rat medullary thyroid carcinoma (rMTC). In this paper we present the results of studies on CT secretion by both the parent tumor in vivo and the rMTC 6–23 cells in culture. CT was measured by a heterologous RIA using antibody against human CT (hCT), hCT tracer, and hCT standard. Complete and quantitative cross-reactivity with synthetic rat CT (rCT) was shown. A progressive increase in plasma CT concentration was observed in rats after transplantation of the rMTC. Tumor CT content was 42 ±5.7 μ/g wet wt tissue (mean ±SE). Intravenous injection of calcium gluconate (10 mg/kg) produced a prompt rise in the plasma CT concentration; no consistent change in plasma CT was seen after iv pentagastrin (5 μxg/kg). Gel filtration studies indicated that the predominant form of immunoreactive CT eluted with [l25I]hCT in both tumor extracts and plasma, although a small peak of higher molecular we...