Expression of Ca2+ receptors in Xenopus oocytes injected with poly(A)+ mRNA from a rat calcitonin-secreting cell line.

Poly(A)+ mRNA extracted from rat calcitonin-secreting cells (rMTC 44-2) was injected into Xenopus oocytes. In mRNA-injected oocytes the intracellular Ca2+ concentration ([Ca2+]i), measured with the Ca2+ indicator dye, fura2, increased in response to an elevation of the extracellular Ca2+ ions ([Ca2+]o). In some oocytes [Ca2+]i transiently increased in high [Ca2+]o but it did not respond to the subsequent alterations of [Ca2+]o. The addition of 10 microM carbonyl cyanide m-chlorphenylhydrazone (CCCP) to the extracellular medium restored the dependence of [Ca2+]i on [Ca2+]o in such cells. It was concluded that rMTC 44-2 cells possessed a receptor which recognizes changes in [Ca2+]o and that these receptors can be functionally expressed by microinjection of messenger RNA from rMTC 44-2 cells into Xenopus oocytes.