Calcitonin was injected in newborn rats and newborn lambs to study the metabolic effects of the hormone. Subcutaneous injection of salmon calcitonin (140 MRC U/kg) induced a clearing effect on plasma from suckling newborn rats that was naturally lactescent. A lower dose given by the same route (14 MRC U/kg) strongly decreased plasma triglyceride and amino acid levels in suckling newborn rats. This was mainly the result of gastric emptying inhibition. The gastrointestinal action of calcitonin in suckling newborn rats was substantiated by the absorption of [14C]triolein and 14C-labeled amino acids. Hormonal changes that were associated were a decrease in plasma insulin level and an increase in plasma growth hormone concentration. Intravenous calcitonin at a physiological dose (0.03 MRC U/kg) injected into newborn lambs inhibited increases in total plasma lipids, amino acids, and blood-glucose levels at the time of the first suckling period without changing serum calcium levels. One of the physiological roles of calcitonin in the newborn may be the regulation of nutrient absorption from milk rich in lipids.

Summary ― The effect of 17!-estradiol on calcitonin (CT) and calcitonin-gene-related peptide (CGRP) secretions in the murine CA-77 C cell line was studied after 1, 3, 5 and 6 d of treatment. The release of both CT and CGRP significantly increased 1, 3, 5 and 6 d after addition of 0.1 Ilmol/l estradiol alone to the culture medium. The C cell content of both peptides also increased after 6 d of treatment with the same dose of estrogen. The enhanced CT and CGRP secretions induced by 17(3-estradiol were not inhibited by the simultaneous addition of 5 wmol/I of all-trans-retinoic acid. Dexamethasone alone increased the release of both peptides within 6 d. However, when cells were treated simultaneously with estradiol and 1 pmol/I dexamethasone, the addition of retinoic acid blunted both the CT and CGRP secretions induced by dexamethasone. These results showed that the positive effects of 17(3-estradiol on both CT and CGRP secretions were modulated by dexamethasone and retinoic acid.CT secretion / CGRP secretion / CA-77 C cell / 17(3-estradiol / dexamethasone / retinoic acid Résumé ― Le 17p-oestradiol à la dose de 100 nmolll augmente la sécrétion et le contenu cellulaire de CT et de CGRP par la lignée de cellules C (CA-77) d'origine murine. Les effets de /'œsfrad/o/ sur la libération de CT et de CGRP dans le milieu de culture sont observés 1, 3, 5 et 6 j après addition du stéroïde. Le contenu cellulaire en hormones est également légèrement augmenté sous cestradiol. L'acide rétinoi'que all-trans 5 wmolll ne diminue la sécrétion des 2 peptides qu'au bout de 6 j, alors que la dexaméthasone 1 pmolll, seule, stimule la sécrétion de CT et CGRP tout au long du traitement (de 1 à 6 j). Si l'acide rétinoïque n affecte pas le contenu cellulaire en CT et CGRP, la dexaméthasone, en revanche, l'augmente. Le co-traitement par l'c!stradiol et l'acide rétinoique n'inhibe pas l'effet du sté-roïde sur la sécrétion de CT et de CGRP. Dans le cas d'un co-traitement par la dexaméthasone et l'oestradiol, un effet additif n'est observé qu'après 3 j de traitement. Le traitement simultané des cellules C par les 3 molécules montre à chaque fois (1, 3, 5 et

Summary ― This study examined the action of 9-cis retinoic acid and 1,25-dihydroxyvitamin D 3 analogues (KH 1060, EB 1089 and MC 903) on the release of calcitonin (CT) and calcitonin gene-related peptide (CGRP) in the rat C cell line CA-77. This cell line mainly secretes CGRP. Using radioimmunoassays (RIA S ) for CT and CGRP, we measured the release of both peptides in the culture medium as well as the amount of these proteins contained in the CA-77 C cells. 9-cis retinoic acid decreased the release of both CGRP and CT dose-dependently in the range between 1 nM and 1 pM. The half-effective dose was 10 nM. The treatment of CA-77 C cells with 0.1 1tM calcitriol alone only slightly decreased the release of both CT and CGRP. The increase in the amount of CT and CGRP released by the action of 1 1tM dexamethasone was reduced by 1 1tM 9-cis retinoic acid, and this effect was enhanced by the addition of 0.1 1tM calcitriol or KH 1060, EB 1089 and MC 903. When the C cells were continuously stimulated by dexamethasone, after 6 days of exposure to the combined treatment with calcitriol analogues + 9-cis retinoic acid, there was a greater decrease in the amount of CGRP contained in the C cells than after treatment with 9-cis retinoic alone. Our data suggested that combined treatment with retinoic acid and calcitriol analogues exerted a stronger inhibition on the amounts of the two peptides either contained in the cells or released in the medium than each hormone alone.