Regulation of plasma calcium and phosphate in calcitonin-infused rats

Enhancement of 1,25-dihydroxyvitamin D3-mediated suppression of experimental autoimmune encephalomyelitis by calcitonin

The active form of vitamin D, 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], suppresses disease development in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS). However, complete disease prevention only occurs with doses that dramatically elevate serum calcium levels, thus limiting the usefulness of 1,25(OH)(2)D(3) as a potential MS therapeutic agent. Because calcitonin (CT) is believed to be released by hypercalcemia and has been shown to be anti-inflammatory, we examined whether suppression of EAE by 1,25(OH)(2)D(3) could be mediated either in part or entirely by CT. Continuous administration of pharmacological doses of CT did not prevent EAE. However, a combination of CT and a subtherapeutic dose of 1,25(OH)(2)D(3) additively suppressed EAE without causing hypercalcemia. Moreover, CT decreased the dose of 1,25(OH)(2)D(3) required for disease suppression. Our results suggest that CT may be a significant factor but cannot account entirely for 1,25(OH)(2)D(3)-mediated suppression of EAE.

The calcitonin gene is expressed in salmon gills

Calcitonin is an important physiological regulator of salmon gills. Although the calcitonin receptor was found in salmon gills, the critical question concerning the source of the hormone remained unanswered. In this communication, evidence is presented for expression of calcitonin mRNA and its encoded peptide in gills of the pink salmon, Oncorhynchus gorbuscha. The expression of calcitonin gene transcripts was demonstrated by reverse transcription-polymerase chain reaction, Southern hybridization, and sequencing. The sequencing identified a sequence corresponding to that of exon 4 of the salmon calcitonin gene. Expression of the encoded calcitonin gene in gills was detected by radioimmunoassay in gill extracts. This synthesis of calcitonin in gills, which also possess specific receptors to the peptide, suggests function of an autocrine or paracrine process producing calcitonin in this tissue. These observations confirm and extend previous reports on the physiological role of calcitonin in fish gills.