Calcitonin mRNA is produced in liver by two different splicing pathways.

Calcitonin, the hypocalcemic hypophosphatemic hormone is produced in the thyroid by the C-cells. We recently detected the presence of calcitonin and its messenger in hepatic tissue in vivo and in vitro. The calcitonin precursor is composed of the N-terminal peptide, calcitonin and a carboxyterminal peptide.

Evidence for receptor-mediated mineralocorticoid action in rat osteoblastic cells.

Aldosterone significantly enhanced the proliferation of osteoblastic cells from rat calvaria, and this effect was inhibited by RU 26752 and ZK 91587, two antagonists specific to the mineralocorticoid receptor (MCR). In addition, aldosterone inhibited the activity of alkaline phosphatase, a marker of the osteoblastic phenotype, and this effect was also reversed by RU 26752. Cytoplasmic staining of MCR was observed in rat calvaria osteoblasts incubated with a specific polyclonal antiserum raised against rat kidney MCR.

1,25 dihydroxyvitamin D and dexamethasone decrease in vivo Walker carcinoma growth, but not parathyroid hormone related protein secretion.

Parathyroid hormone related protein (PTHrP) is produced by several breast cancers. 1,25 dihydroxyvitamin D (1,25[OH]2D) and Dexamethasone (DEX) have been shown to decrease PTHrP mRNA expression in several cell lines. We therefore tested the in vivo effect of both steroids on PTHrP secretion and tumor development of the Walker carcinoma (WC).

CGRP is expressed in primary cultures of human hepatocytes and in normal liver.

We recently reported that human liver and primary cultures of hepatocytes express calcitonin. We therefore studied the expression of calcitonin gene related peptide (CGRP), the alternative splicing product of the calcitonin gene, in hepatocytes and liver. We used polymerase chain reaction amplification with specific primers to detect the presence of CGRP I and II messengers and a specific radioimmunoassay to measure the peptide.

Calcitonin genes (I and II) expression in human nervous and medullary thyroid carcinoma tissues.

The calcitonin gene family comprises two main genes: CALC I which encodes for calcitonin (CT) mRNA in thyroid and calcitonin gene-related peptide I (CGRP I) mRNA in neuronal tissues and CALC II gene which encodes for CGRP II mRNA only. Recently, in normal thyroid and in medullary thyroid carcinoma (MTC), we detected an additional splicing pathway involving the splicing of exon 4 to exon 5 and leading to the expression of a third CALC I mRNA: CT mRNA II. In the present study, we analyzed by polymerase chain reaction the expression of CT mRNAs I and II, CGRP I and II mRNAs in MTC and in human tumors of the nervous system (3 pituitary adenomas, 3 astrocytomas, 2 schwanomas).

Calcitonin gene expression in normal human liver.

Immunoreactive calcitonin (CT) is present in liver. This could represent hormone synthesized by liver cells, degraded or bound to specific receptors reported in this organ. We report here that the calcitonin gene is expressed in liver.