Ipriflavone inhibits phosphoinositide hydrolysis and Ca2+ uptake in the osteoblast-like UMR-106 cells

Comparative effects of eel calcitonin, salmon calcitonin and [Asu1,7]eel calcitonin on hypophyseal and osteoblastic function

Three different calcitonins: salmon calcitonin, eel calcitonin and the semi-synthetic analog [Asu1,7]eel calcitonin have been evaluated for their ability to affect phosphoinositide hydrolysis in primary cultures of anterior pituitary cells and in the osteoblast-like UMR-106 cells. In both cellular systems a repeated treatment with any form of calcitonin induced an inhibition of inositol phospholipid turnover. Eel calcitonin and its analog were always more potent than salmon calcitonin, but the efficacy of the three polypeptides was comparable. In cultured anterior pituitary cells, the inhibitory effect on phosphoinositide hydrolysis observed after chronic treatment with calcitonin was accompanied by a reduction of prolactin release. In contrast, a single treatment of cultured anterior pituitary cells with eel calcitonin or its analog [Asu1,7]eel calcitonin induced an increase of inositol phosphate accumulation, while salmon calcitonin was inactive. Accordingly, eel and [Asu1,7]eel calcitonin, but not salmon calcitonin, induced a slight but significant stimulation of prolactin secretion. In UMR-106 cells, the three calcitonins exhibited similar potency and efficacy in reducing parathyroid hormone-stimulated 4 beta[3H]-phorbol-12,13-dibutyrate ([3H]PdBu) binding, an indirect index of protein kinase C activation. Taken together, these results suggest that, either at the pituitary or in osteoblast-like cells, some of the effects exerted by calcitonin may be ascribed to an interference with the intracellular events initiated by modulation of phosphoinositide turnover.

Ipriflavone and low doses of estrogens in the prevention of bone mineral loss in climacterium

Estrogen replacement therapy can counteract all postmenopausal symptoms. While low estrogen doses (0.15-0.30 mg of conjugated estrogens/day) can counteract neurovegetative and psychological symptoms, higher estrogen doses (at least 0.625 mg of conjugated estrogens/day) are required to prevent bone mineral loss in postmenopausal women. However, if contra-indications to high estrogen doses exist, drugs other than estrogens can represent a suitable treatment for postmenopausal osteoporosis both alone or in combination with low estrogen doses. Experimental and clinical data have shown that ipriflavone is effective in the treatment of established postmenopausal osteoporosis. With the purpose of evaluating whether ipriflavone is able to enhance estrogen activity on bone metabolism, 133 postmenopausal women were randomly submitted to the treatment with: (1) placebo; (2) 0.15 mg/day of conjugated estrogens; (3) 0.30 mg/day of conjugated estrogens; (4) 0.15 mg/day of conjugated estrogens plus 600 mg/day of ipriflavone; (5) 0.30 mg/day of conjugated estrogens plus 600 mg/day of ipriflavone. One g/day of calcium supplementation was given to all women. In all subjects bone mineral density was measured before and after 6 and 12 months of treatment at the distal radius by dual-photon absorptiometry. A moderate decrease of bone mineral density was evidenced in women submitted to placebo or to estrogen therapy alone. By contrast, an increase of BMD was measured after 12 months of treatment in the women treated with 0.15 (not significant) or 0.30 mg/day (P < 0.01) of conjugated estrogens associated with ipriflavone. Both dosages of conjugated estrogens were able to induce a significant reduction of neurovegetative symptoms. The increase of bone density obtained with the combination of conjugated estrogens with ipriflavone demonstrates that this combination improves the effects of low estrogen doses on bone mass representing a satisfactory approach in the prevention and treatment of all symptoms related to the climacteric syndrome.